Re: BOV is opening under boost
 

Herein lies the stupidity. You are NOT making over 12-psi, you yourself underlined no more than 6-psi for your cast setup, correct? You yourself stated your engine allegedly makes 500 naturally aspirated, correct? So no more than 6-psi, correct? That being said, why did you single out the "race" valve, ehh? Why not share where the STANDARD valve connects to, which would be for your application, which is why I added it? Your car hasn't even seen any times yet, and can't even hold boost, so where do you get "race" valve from lol...?

" Both the inlet and outlet mate to a 1 in. hose"...

"They help eliminate compressor surge and reduce heat soak in the discharge tube"...

https://www.summitracing.com/parts/v...yABEgLGJfD_BwE

https://static.summitracing.com/glob....jpg?rep=False

Like I said, stop listening to the soy boy above, he probably touches himself while writing these posts, and to borrow a quote from Deniro, he is making your mind into mush... :lol:.

- Rob

Re: BOV is opening under boost
 

I really hope you are better at finance than reading comprehension.

I'm not making more than 3 psi because my Greddy Type S BOV is opening under boost and dumping my boost.

But beyond your lack of reading comprehension, the bigger problem is your lack of understanding of volume vs pressure. But beyond that, pointing back to your lack of reading comprehension, you've failed to read the manuals for the system. I realize this is because you don't have any experience with the system and are cherry picking information from google searches. I've gone ahead and underlined the important data right from the manual supplied by vortech for my "RACE" head unit (which is clearly marked RACE on the tag, rather than a street head unit):

https://cimg1.ibsrv.net/gimg/www.thi...baea68ac4c.jpg

Now you are probably wondering how do I know if I'm spinning the impeller beyond 41,000 RPM? Well because of math:

https://vortechsuperchargers.com/pag...eed-calculator

7.8 " crank pulley, 3.33" supercharger pulley, 6,200 RPM = 50,000 rpm impeller speed. Even if I shifted early at 6,000 RPM that would put the impeller at 48,000 RPM which is a larger number than 41,000. (You are a finance guy right? Surely you know math).

Lastly, you still seem stuck on the whole concept of where the dumped air should go, and again I'll point to the manual. I've underlined the important information once again to aid you:

https://cimg2.ibsrv.net/gimg/www.thi...40c5fa957b.jpg


-- Joe

Re: BOV is opening under boost
 

Seriously, this is why credible members stopped posting in this thread. The engine in question here is a cast setup, and cast parts are good to maybe 500 horsepower, and that is pushing it. Direct engine, different story, but we're talking an old school SBC here so spare me the comprehension lecture. Naturally aspirated the engine is already close to that from what we are told, so boost pressure cannot exceed 6-psi of pressure unless you want to break a piston or bend a rod. So why the hell is the OP talking about 12 PLUS pounds of boost pressure lmao while justifying a race BOV? Do you know what 12 pounds of pressure equates to with a naturally aspirated engine making close to 500 horsepower? Hmm lets see, 500 times 84 percent will give you 420 ADDITIONAL horsepower. Are you running 920 horsepower that would justify the race valve? I think this pretty much sums it all up. The standard bypass valve is good for low boost pressure, which is what this engine will be seeing. If you "choose" to go with a race valve because you are convincing yourself the engine is making that much, then that is just your choice. So vent away to the atmosphere if it makes you giggle, while making you feel all warm and cozy inside. You do realize they also make hybrid bypass/bov's, right, covering two birds with one stone? So if you have the added need to vent away to the atmosphere like the cows do a la Alexandria Cortez, then release the evil if it makes you happy lol...

- Rob

Re: BOV is opening under boost
 

The engine (412" SBC = 400 block bored .060 over) has a forged steel crank, forged pistons, and eagle rods. You are confusing this with the LT1 in my C4.

What 'credible' members?

Boost is a measurement of restriction. This isn't your TPI intake on stock heads. This is a ported miniram on AFR 210 heads.

If you want to gauge performance you need to do it by measuring air flow.

Again, showing that you don't understand volume vs pressure. It doesn't matter if the engine is 200 hp, 500hp, or 5,000 HP. When the throttle blades are closed the air needs some place to go. If the air cannot escape through a hole quickly enough it will try to force the compressor blades to spin backwards.

I've provided you with documentation, math, and explanations. It's ok to admit you don't understand Rob. You should try to learn something new every day.

-- Joe

Re: BOV is opening under boost
 

This is what it comes down to, anyone reading this will agree except those who need to inflate their own ego like the imported LSX ebay turbo dumb@ss up above;

"My BOV is opening under boost"

.... invest in a BETTER blow off valve.

"My BOV is sneezing during discharge"

.... invest in a LARGER blow off valve.

Simple enough, no? Now, it does not matter "if you agree" with what I just wrote because that is the bottom line. However, it is clear that you don't quite understand how a bypass valve eases the back pressure of forced resistance. A bypass valve works up to a certain point when it has no choice but to be vented to the atmosphere. That is when resistance is just too great to be recirculated, but you are nowhere near that level. If you make 6-psi at 5000-RPM running a 3" charge tube(s) and 3" Intercooler, but then suddenly swapped to 4" charge tube(s) and a 4" Intercooler, do you honestly think you will still be seeing the same 6-psi at 5000-RPM? Of course not, because you increased its' volume in the tract. You reduced resistance. A bypass works in the same manner by creating more volume when the throttle suddenly closes through recirculation, but it only works well up until a certain point (obviously), but again you are nowhere near that level, and if you are trying to convince yourself that you are, then that is on you.

- Rob

Re: BOV is opening under boost
 

You are aware that that was covered and decided on post # 36 on 5/9/2019.

You still don't understand volume vs pressure, and still think I'm running a turbo.

Absolutely everything has been covered in detail numerous times by myself and others. Re-read the thread and learn. Then apply what you have learned to your project.

Is the GTA turbo now? Naturally aspirated ? Big procharger? I forget where you are with that project. I know it's a 9 second TPI.

-- Joe

Re: BOV is opening under boost
 

Lets recap Joe; you're running 60# injectors at 72% DC, which is roughly 630 Horsepower. You were seeing 3.2-psi of boost pressure, which is about a 21% increase, so at 630 horsepower you would be making roughly 520 naturally aspirated, and these are all flywheel numbers of course, not to the wheels. That extra 110 horsepower at 3.2-psi of boost pressure equates to approximately 76-cfm. When that throttle suddenly closes, all that is left is that 76-cfm at 3.2-psi of boost pressure, which is rapidly decreasing not just with help from the IAC port and bypass valve, but due to the decreasing RPM. Are you really that concerned with 76-cfm of boosted resistance upon the throttle snapping shut? Hell, these blowers were designed to take a resistance beating from way more than that with an open throttle for crying out loud. Not to mention, exactly how high in boost pressure are you planning on going with your setup? I'd be more worried about your engine blowing first than the blower. Just so you know, I am more than aware that bypass valves are typically made on the smaller side compared to BOV's, so I can see why they may be a concern for you...

- Rob

Re: BOV is opening under boost
 

Maybe, maybe not. Who knows what the BSFC is, or the impact of a rich/lean AFR. I'm not sure that strictly using injector duty cycle to calculate engine output is a sound scientific method.

But I don't think the motor makes 520 hp NA. Probably more like 420-450.

You also can't arrive at 21% increase by using boost pressure alone, you need to know what the air flow is.

This is where your math goes way off course because you are trying to determine CFM from boost pressure. It doesn't work that way.

When the throttle suddenly closes at say even 5,000 RPM the impeller is moving at 40,000 RPM.

If you look at the compressor map / specs for a t-trim as shown in post #22, you'll find that the t-trim is pushing about 872 CFM at that impeller speed.

If you think that the impeller spinning at 40,000 RPM only produces 76 cfm well.. I don't know what to tell you.

Sure the RPM decreases and so does flow, but the RPM doesn't decrease faster than the throttle blades closed, and the IAC should also be closed because the engine is ABOVE idle speed not below it.

But even if the IAC was fully retracted, if you think the the 1/4" IAC passage is large enough to dump the compressed charge you are crazy. The Type S Bov outlet is 29MM (1-1/4")

Again, there is two problems going on here:

1) The BOV is opening under boost, and leaking some of the compressed air, resulting in only 3.1/3.2 psi seen in the intake manifold.
2) The BOV is not large enough to dump the full charge when the throttle blades are closed, leading to compressor surge, as it's only 29MM.

You should buy a supercharger and get some experience with it.

-- Joe

Re: BOV is opening under boost
 

Just so we're on the same page here, consider how much air is being taken in by the IAC. Forget about your blower for a second, and think about your C4 Corvette. I will be as "dramatic" as possible, Hollywood style; It's a dark and stormy night, and you're out running on an essentially abandoned highway, or so it seems, when suddenly.... you see something jump out in front of you. Was it a deer? Was it a wolf? Or maybe, just maybe, it was a ghost!!!! Whatever it was, it seemingly forced you to lift your foot completely from the throttle out of fear at 6500-RPM, slamming the throttle blades closed! Mind you, the engine is still momentarily spinning at that same RPM during decel when you lifted, and is going down slooooooowly. However all that needed air being pulled in from the pistons is still being taken in through the IAC valve at that RPM. All of it! Though, the engine is decreasing in RPM fast, and the injectors are shut down, but the air is still being taken in. Do you have any idea how much air is being taken in through the IAC when you lift at high RPM's after slamming the throttle blades closed? Well lets put it this way, if the IAC were too small a pathway, your engine would implode! So yes, the IAC helps to alleviate compressor surge along with the bypass valve. Obviously it cannot alleviate all of that added boosted resistance from the blower on its' own, but it does help, because air is still being taken in by the engine after the throttle blades close. This is just one of those; "the more you know" adages...

- Rob

Re: BOV is opening under boost
 

I'm not sure whole told you this, but regardless of what my foot is doing, the IAC is completely closed at > 1500 RPM. I've verified in my log it is absolutely 100% closed, as I told it to do in my tune.

I can't speak for your EBL, I know some GM masks have a 'throttle follower'.

-- Joe

Re: BOV is opening under boost
 

Your engine is gonna implode from too much vacuum..... Thats a new one. what evidence do you have that supports this? Cant say I've ever heard this.

Re: BOV is opening under boost
 

Heard what? An engine, an air pump, spinning at 5000-RPM.... when suddenly closed/stopped and no longer has an adequate air source, just stopped by closing its' air supply, do you honestly think the gaskets won't tear apart? Are you serious? What did you think I meant when I said implode? Never said explode, if that is what you're getting at...

- Rob

Re: BOV is opening under boost
 

This thread is reaching comedic proportions. I don't know much about superchargers, but half of what Street Lethal makes no sense at all :lol:

Re: BOV is opening under boost
 

... so, if the engine in question is taking in 347-cfm at 5000-RPM (500 horsepower) naturally aspirated, and the throttle blades are suddenly closed, you are no longer making 500 horsepower because fueling is halted, however you are still momentarily taking in the same usable cfm (potential horsepower) because the pistons and valve train are still spinning at that speed. So if the IAC can handle upwards of that much cfm as the engine is decelerating, are we to believe that it cannot help to offset that amount by 76-cfm going the other way (3.2-psi of boost pressure) in your particular application? Hmm. I guess slapping on a BOV without understanding every other angle is the easy way out for most. But then again. I mean hell, if anything, the BOV is making the IAC's job easier, not the blower lol. Meaning the BOV will make that noise either way because it is a targeted pressure leak. It goes back to my first question, plug the BOV and tell me where your kPa is during idle, and part throttle.

- Rob

Re: BOV is opening under boost
 

Are you running a blower? Or are you just an LSX nut swinger?

Don't expect you to understand, believe me lol...

- Rob

Re: BOV is opening under boost
 

Pages and pages of opposition, yet nothing gets fixed. I keep pulling myself from work because it is very very amusing reading these comments from everyone, because everyone seems to know everything, meanwhile the problem persists. I think Joe just likes conversation, even with the $60 code. It went NOWHERE, but the discussion was fun to him I guess. Funny thing is, I really did call Vortech because I was very curious since it is their unit, and they said EXACTLY what Diggler originally said, "this guy needs a bypass valve, his BOV is set too soon or is just bad to be controlling anything"...

Anyways, I'll leave you ladies to your beliefs.

- Rob

Re: BOV is opening under boost
 

Again, reading comprehension is failing for you, or you just don't understand what people are telling you.

I ordered a new valve on 5/9/2019.

Still waiting for your technical explanation of why a Vortech should have the valve discharge routed back to the intake. I've posted the documentation from Vortech. As stated by vortech, it's only routed back to the intake for MAF applications.

Again, I've posted the manuals, I've underlined the sentences. You can re-read them over and over again until you 'get it'.

I don't know why you are bringing up the $60 code. That was Bruce's project, and I was probably one of the only people who actually ran it in a track car. That was before you even joined thirdgen.org


-- Joe

Re: BOV is opening under boost
 

Me being a "LSx" "nutswinger", or not, is irrelevant. I do plan on running one in the future and from what I have read elsewhere, you don't know what you're talking about.

anesthes is posting legitimate facts and you're posting nonsense and contradictory statements sometimes. Everything Kingtal0n posts also makes sense, you, not so much.

As I said, hilarity on your end, I wouldn't expect you to understand, believe me :lol: I look forward to what you reply each time I see this thread has a new post :thumbsup:

Re: BOV is opening under boost
 

I never said explode either. Your the only one that said explode actually. If you do think engine implode from excessive vacuum, than how do AC systems contain well over 30inches of vacuum before a charge? They have rubber lines, they dont implode, but a cast iron block and gaskets will? head gaskets and cylinders suffer 2500* temperatures and sometimes up to 200 psi of static cranking pressure and dont have issues. I think they will be fine with vacuum. Alot of newer engines use rubber intake gaskets and they idle at 20-23in.

This thread is getting out of hand. lol

Re: BOV is opening under boost
 

So the new BOV absolutely fixed the surge issue when closing the throttle. Thanks Dan!

Boost is peaking at 3.3 psi at just under 5,000 RPM. I repeated this a few times.

The only thing is it starts breaking up right around there so I back off. I'm not seeing sync loss and it's not going lean so I'm not sure what that's about.

One thing that has me concerned is the injector duty cycle is at 91% which.. Is a ton of fuel. It's 65 degrees out and the max rise is 81 degrees, which tells me the intercooler is effective.

The BOV is open now 100% at idle and most driving. You have to 'get on it' to get it to close and then it builds boost. At idle, before even driving the car, if you put your hand around it it blows HARD and HOT air. So I'd say it was a good purchase.

https://cimg8.ibsrv.net/gimg/www.thi...fd73aa4afe.jpg

Re: BOV is opening under boost
 

At this point. If you haven't done it yet. I would perform a pressure test of the system from compressor cover to the engine. Disconnect fresh air from crankcase and fill plumbing to 15~psi of pressure using air compressor in a quiet place where you can hear leaks. It should hold pressure till you let it out, more or less. At least hold for 10 seconds or so.

There are always leaks to deal with. And you need to be sure the Bypass is set properly to be sealing at high pressure.
Every air molecule that escapes the plumbing between the compressor and the engine is lost power and increased IAT so it is an essential step for FI.

As to the blow-out. It may simply be spark blow out (often set the plug gap 0.026" to 0.032" for 10-12psi of boost). Or tuning related. If the engine is highly modified maybe take a couple degrees out (I see 20* when maybe 16* would be superior)
With hot air, and especially boost, the timing needs to come way out of it. 16 in places you would normally use 24. 12 in places you would put 20. On pump 93 around 10* works out well for 15~psi of boost pressure most setups approaching 95% VE with aluminum heads around 9.5:1 compression. I wouldn't depend on the knock sensor either. Take out timing till EGT skyrockets or torque values plummet (dynometer) and add a little back to keep it off the EGT ramp and preserve within 5-8% of max torque. Leave timing on the table for future situations that are not ideal (i.e. bad gas, going uphill, passengers and weight/load, etc... all requires less timing than optimal for peak power on a dyno)

Using those engine stats I would want to see about 12:1 at 0psi, 11.5:1 for 0 to 7psi, 11.0~ for 7-12psi and 10.8~ range for 12-15psi on 93 fuel with IAT < 105*F

The hotter the air gets (higher IAT) the less timing you will want. And the more EGT will raise. At such low boost it wouldn't be an issue. The issue crops up when IAT starts to pass about 110*F due to intercooler heat soak or just plain blower heat soak (roots blowers) and the increasing IAT causes more timing reduction which results in even higher EGT and so forth in a never ending loop. The fix is either superior fuel, better intercooling, or water injection. With a good intercooler it should be possible to hold near Ambient air temps (within 20*F or so I would guess for blowers) turbos have it much easier apparently.

Re: BOV is opening under boost
 

totally depends on which head and how small the cam is. Some chambers are slow some are much faster. My small cammed small afr head liked 14-16 deg on pump. My big head big cam same everything else just about ran 22 deg at 24 lbs. boost lol wasnt making cylinder pressure til way up high tho.
Wot no boost i always go mid high 12’s afr. 1-5 psi low 12’s to mid 12’s. 5-10 high 11’s low 12’s. After 10 let car decide, mid 11’s is generally safe but depends on the combination lol. I never been much below 11.4:1 afr except in hot iat

if your ignition is good it shouldn’t be blowing spark out at 3 psi boost lol plug gap down to mid 20’s should handle it.

Re: BOV is opening under boost
 

I used to run my car on 6 lbs at 12.5:1 afr till i took it to a dyno day at a local shop. guy freaked when he saw 12.5 half way through first pull. (pump gas around here is E10) he let me fatten it up a little bit to a 12.1 and it picked up 16RWHP across the board. Said in his experiance, 11.0 in my boost range, on pump gas is the spot I wanna be. Never went back, but when I eventuially get boost up to 10 lbs, I'll be renting some dyno time from him.https://cimg9.ibsrv.net/gimg/www.thi...ccbfff8b32.jpg

Looks like your out of injector though.On a side note, I'm running completely stock ignition other than ceramic end plug wires and shorty plugs which are @ stock .035 gap without issue so I don't think your issue is ignition system. I think its fuel on top of your either boost leak or belt slip. Got a fog machine?

Re: BOV is opening under boost
 

Yeah I was thinking about how about doing that. I guess make some plumbing fittings for a gauge and valve like I'd test a gas pipe.

If it was naturally aspirated with this cam and heads I'd probably run around 32-34 degrees total timing. So although the intercooler is effective, I've set it to it's around 28 degrees in the current boost range. If boost creeps it will retard to 25 or 22. Going on Prochargers literature, they don't recommend retarding at all if the intercooler is effective. I actually thought I was playing it safe for now lol.

https://cimg4.ibsrv.net/gimg/www.thi...1fe2fc2bce.jpg


That's about where I am for now, maybe a hair leaner it looks like around 11.8 if you trust the wideband. I could add some more fuel to be safe. Plugs are gapped to .034.. maybe that's too wide, although you'd think with CnP it would be a good hot spark.

-- Joe

Re: BOV is opening under boost
 

Could very well be fuel. I'm running 93 pump. I'd be shocked if my ignition was failing being it's a coil per cylinder, although I should probably investigate it.

This is the intercooler I'm running. It says it's rated for 1000 cfm / 800 HP, although I wonder if maybe it is a flow restriction..

http://www.frozenboost.com/front-mou...ger-p-202.html

-- Joe

Re: BOV is opening under boost
 

your running a V1 T trim right? 55K max RPM/ 26PSI max / 1400 CFM max? if your spinning 50K it might be more CFM than it can handle. I wonder if thats why its not boosting? More pressure in the pre intercooler charge pipe than there is on the back side of he BOV?

Re: BOV is opening under boost
 

I've never tuned an 'old' (2-piece) motor with that much boost. However that timing table is far too much for any LS engine even an N/A LS motor.
Modern combustion cylinder heads don't require much timing. A naturally aspirated LA motor around 500rwhp NA uses approx 23-24* of total timing.

Anything over 10* on pump 93 at 15psi is pretty much unheard of, a death sentence. The only motors pushing 11,12,13 on pump fuels are using methanol injection and even then I don't recommend it.

the way to tell for sure is like I said already, EGT & Torque. Either get a gauge or a do some dyno pulls with and without a couple degrees.

Next,
Try smoothing that timing table out once you get it dialed in. I never leave the same number in a cell, next to another cell.
This reasoning comes from dealing in digital electronics. Imagine the engine is moving 5000rpm (how many sparks per second is that?) And you ask for exactly 20* of timing.
Now lets say you could measure every single spark to check how far off from 20* It is:
20.005*, 20.007*, 19.998*, 19.989*, 20.014*, 20.002*, etc...
Notice how it goes back and forth between 20+ and 20- , because it cant actually perfectly nail 20* every single time (in reality) there is always some error.

The reason this is so important is because of the acceleration of the engine. If the engine dRPM (Rate of change of RPM) is positive, it means the engine is accelerating, which means the next piston event comes even sooner than the last one did. In your mind you should already realize this means more timing will be required, the faster the engine rate goes the more timing will be necessary to 'keep up'. Yet, if you're only asking for 20 20 20 20 across the board, the dRPM will oscillate and the torque/power output of the engine will appear wavy and oscillatory.
The fix is to make sure that every cell has an incrementally changing timing number, it should increase just like a distributor does until peak torque region, then soft spot through peak torque, then back up to make use of whats left of the VE as it trails out to redline, increasing timing as RPMS rise after peak torque as necessary. The necessary timing after peak torque depends on how fast VE drops, and the rod ratio (piston dwell), fuel quality (Pump fuels when hot burn 'fast', use less timing), that stuff

And fueling wise, leaner is not meaner. More fuel = more fuel molecules to interact with oxygen = more pressure being built after the spark occurs. Which is why you don't want a whole bunch of timing when you've got the fuel mixture dialed in plenty rich enough, the pressure will escalate the fastest it ever will and if the piston is anywhere near TDC it will hammer the rod bearings and stress the piston ring lands without every setting off the knock sensor, because it isn't detonating/knocking, its still burning like its supposed to, its just burning at the wrong time (too early)

Re: BOV is opening under boost
 

He has a small block chevy. Not everyone builds ls motors

Re: BOV is opening under boost
 

It has do with the design of the combustion chamber, and piston, and the space between them, and the space between the cylinder wall and piston. That stuff factors in, and if the company that makes the heads has 'copied' the efficient designs (from LS engines or Nissan engines or Toyota engines, etc... they are all efficient after 1998~2002) then it will/may need to be timed as such.

Re: BOV is opening under boost
 

Its not an ls head. Its an afr head. I have used them and boosted them. I know what they tend to like

Re: BOV is opening under boost
 

I could always argue that the total timing will depend on the temperature of combustion, there is no one set number that fits every single temperature the CC will experience.
It may prefer 28* when cool (450*F) driving around and you hit it.
And then it may prefer 18* when fully warmed over (1500*F Wot pull in overdrive)

The thing is, we only get to choose one number for both situations. Because nobody's timing map has compensation for high EGT (well some OEM do but not in this case)
So the number chosen must reflect the worst possible conditions (lowest octane and highest temperature) the engine will ever see.

Re: BOV is opening under boost
 

you would probably see around 30" of vacuum in the manifold, you cant get any more than that. as stated, some stock cars idle at 22-23". no biggie, the car would just cease to run if it cant get enough air.

Re: BOV is opening under boost
 

Haha, you of all people know what I was getting at, but perhaps I should not have used the term implode because it was a little too drastic. Think about it though, consider an engine running 6000-RPM wide open throttle, but the throttle blades suddenly slam shut and the IAC is stuck closed. Again, implode might have been too drastic of a word, but the gaskets would be compromised because the pistons are still momentarily pulling in air just prior to the engine stopping with no air source, so it's gotta come from somwehere prior to locking up. Point I was originally making was the IAC does at least help bleed off some of that charge when the throttle blades close on decel. Its' most certainly not the savior for compressor surge, but it does help relieve the pressure. But at any rate, I do agree with what you said earlier Dig, he needs a bypass valve. Running the BOV with the bypass is up to him, but basing it on what we were being told, 3.2-psi, with no alleged ignition problem, and no alleged boost leak, I just don't see that much pressure being worried over. But hey that is just me. The other stuff being discussed in this thread is just unrelated and takes away from the issue getting resolved, which is something I think we all would like to see, getting resolved. So just fix it and lets see what happens from there...

- Rob

Re: BOV is opening under boost
 

Thats true to a point, theres a difference in what the tune up will look like for a land speed car vs drag car vs street car because time in throttle will change chamber temps. Chamber temps are not exactly EGT by the way, EGT is post chamber and could be greatly influenced in sensor placement and timing. Too retarded and combustion can take place in the exhaust and not the chamber.
you are throwing out generalizations here tho, and not looking at the specific scenario here.
We know the combo. We know its use is street driving with occasional short wot bursts. Maybe a 1/4 mile pass here and there. We dont need to concern ourselves with the long term chamber temps beyond a wot 1/4 pass. 10-12 seconds max. This is 95%+ of the people on this forum. The tune isnt too difficult to find
You can tune that doing dyno pulls to find max power which would be max cyl pressure for the given rpm. Then to be safe you pull 2-3 deg and head to the track to test. Same with fueling. Find max power air fuel and then typically we richen it up slightly to keep it safe then test on track.

The sbc has been around for decades. This has been done many times and they all seem to end up in the same ball parks for tune ups.

Re: BOV is opening under boost
 

Nah,
1. DBW cars do it all the time without an IACV.
2.Full vacuum decel is an issue in certain racing venues, I think circle track has the issue, and it wouldn't have any affect on the engine's sealing, I think it sucks the rod off the crank or something and damages the rod bearing. Something like that.
3. Engines with IACV typically open the IAC with the throttle blade, so when the throttle slams shut the IAC is mostly wide open and gradually closing so the idle comes down softly (but this can be tuned out)
4. Finally and most important. The column of air which has been accelerated towards the engine at some rate, lets say 800CFM, Exists the moment the throttle valve shuts, and now whether there is an IAC or NOT doesn't make a difference because the engine Flow-Rate is set to some number typically seen around idle (say, 100CFM) which means the leftover airflow-rate needs to go somewhere. Where does it go? If there is no pressure-relief valve, it has been known to bend throttle shafts, that sort of thing. In other words, the minuscule flow of the engine when returning to idle from a WOT pull is negligible and useless for relief of the pressure.


1. I use EGT as a measuring device because for most of us (and the thread op, hobbyist stuff) we don't have a direct means to measure the actual chamber temps.
2. Yeah being able to say 'its just a race car' really takes alot of work out of the tuning process, okay
3. I've heard that creativity can cover for lack of knowledge, or that there is a difference, and sometimes it's okay

Re: BOV is opening under boost
 

2: noone said that. But you tune for the use of the car. You put in as much time as you think it needs to satisfy your requirements.
3: no idea what you are saying here and why that is relevant to the thread.

Re: BOV is opening under boost
 

it wasn't meant to be negative. I just mean that, sometimes we have a method in our head that is 'imaginative'. And if we use that method on a machine, and the machine seems to run fine afterwards, then great I guess.

In reality, we can't really tell or justify the tuning for an engine without being able to analyze the right data, and properly at that.
EGT data for example basically tells nothing exact, because of placement and error.
Dynometer tune for best torque output (mean best) is no longer optimal once the vehicle is loaded by its own weight and in various gears/time periods/climates/hills/varying fuel quality.


To even get close to the right data, it usually includes some form of combustion pressure analyzer which none of us have access to (yet, they've come down low enough in price though that someday soon it might hit hobbyist level)

So 'be creative' and maybe its okay, it will probably be fine, but it is by no means 'exactly right the way as it is in human mind'. Not unless the human can properly analyze the right data and form fit to a theoretical model. Like a space ship I guess. But thats everybody- its just a limit of human intervention. Nobody is blaming tuners that don't own those tools.
I suppose its why experience is so important.

Re: BOV is opening under boost
 

TFX Engine Tech has combustion pressure monitoring for hobbists... but your average joe does not need this lol

Some dynos however can load more than a cars weight on the road, but most dont. Dyno gets you close, final tuning takes place during the activity in which you are engaging. I dont consider it creative or imaginative but to each his own lol its a tried and true method that works long before computers were invented lol reading plugs and racing heads up

but do your own thing and use whatever methods and tools you feel are necessary.

Re: BOV is opening under boost
 

The engine will run well between a wide range of settings. Some computer stand-alone systems only adjust timing in increments of 1 integer, i.e. 8, 9, 10, 11, etc...

But you have to stop and ask yourself. When is the optimal timing actually going to be exactly 10.00 degrees? What are the odds of it being perfect exact 10 10 10 10 10 10 for hundred thousands of cylinder events in a row exactly 10.00 it will almost never happen.
So no, we aren't getting exact with our numbers, there is always error. There is a range where any number between this and and that will work, a range inside error term. Some engines have superior regions for error. Unimaginably wide ranges of timing are acceptable on 2.0L engines using 93 octane at 35psi of boost pressure.
https://www.evolutionm.net/forums/ev...l-project.html

I've seen close to 7* of timing in the same situation but with methanol injection. When did 7 become 0? Really zero at 3500rpm the 2.0L engine is making 350ft*lbs or whatever V8 torque?
When do you know 0* and when 7, just like when do you know 24 and not 32, when is 9* and not 13*, those dangerous spread of acceptable numbers: 14 and toast. 33 and toast. 6 and toast.

Re: BOV is opening under boost
 

How much tuning do you do?

Re: BOV is opening under boost
 

i dont kno maybe around a hundred cars total,

almost one of everything
no bmw or 4g63 yet

in 2001 my daily was a 2-piece rear engine, stealth ram twin turbo 355, stand-alone holley
wheres waldo
got a video somewhere

Re: BOV is opening under boost
 

The first thing that dawned on me when I read this was that I was pretty sure the Holley Stealth Ram was released in 2002 not in 2001, and I also wasn't aware that Holley offered any type standalone system that handled boost back then, it was usually just for a naturally aspirated system in their case, and even then they weren't that common. Accel and FAST were normally the go to brands for the standalone guys running boost, and chip development was obviously still underway on this board back in 2001, with Bob and Bruce still heavily involved in the GN world. Meh, but I figured I would give it the benefit of the doubt and search the Holley Stealth Ram and standalone ECM to see if guys had that availability back in the day, just out of curiosity. As fate would have it, I came across this post from you in April of 2004, three years after what I quoted from you above of already having an HSR in 2001...;

https://www.thirdgen.org/forums/alte...ml#post1787152

You know... I'm not being sarcastic when I say this, and I really don't have time for nonsense in my life which is why I stopped arguing in this thread, but after reading this from you and being curious and running a search, then hearing something entirely different from you from fifteen years ago, three years after what you're saying now, then why not just tell Justin that you tuned about thousand cars total instead of just one hundred? Yeah, sure, I mean throw in a few fighter jets while you're at it. Yeah, yeah,I tuned the fighter jets Bush sent into Iraq, yeah yeah that's the ticket. I mean, saying you ran a twin turbo SBC with a HSR powered by a Holley standalone back in 2001 as a fact, but then buying your first HSR in 2004, is obviously quite the feat for anyone unless they were Marty McFly....

But I digress, of course. Happy Memorial Day fella's...

- Rob

Re: BOV is opening under boost
 

wow like i remember exactly what year it was when i had my first high performance intake manifold

So I can't remember exactly 20 years ago what day I had this or that engine. This is why I keep pics and videos because I do NOT remember yesterday.

Thats what searching is for, 1 quick button and wham
https://www.thirdgen.org/forums/powe...ml#post1923821

Looks like 2004 then. Ok so, I took a guess of 01' and it was 04' instead, sue me?
What do you think I actually remember the year I received every single part?
You obviously love to attack people for simple spelling mistakes and that kind of bullshit.
I guess your memory must be perfect.

How petty and disappointing.

Re: BOV is opening under boost
 

Before youtube was invented i had a digital video recorder and was filming stand-alone tuning

This is from before the stealthram, so 2001-2003

This is from before that

and this is from before that

And this was before that

Pretty sure I have some of the oldest videos on the internet of V8 engines, cam and engine swaps, stand-alone tuning
It starts getting good here when I switch to 2.0L

more power from 4-cylinder engines at the time. What is that 2005? 2007? Around 10 years ago, about 9 years after building the first V8 engine (or was it 7? gee idk)

point is there is plenty of pictures videos and proof that the year isn't relevant within an error of ~3 years if the range is over 20 and human memory is useless after a day or two (yours isnt?)

how many videos can I even fit here

Re: BOV is opening under boost
 

found the turbo video on another account

Lets look back at 07 for a minute because that was the year of many things
https://cimg8.ibsrv.net/gimg/www.thi...72e3f45cd5.jpg
https://cimg1.ibsrv.net/gimg/www.thi...c3fbd6a480.jpg

This is a right hand drive 2001 Supra. They stopped making them here in 98 but in Japan it kept going till 2002.
https://cimg3.ibsrv.net/gimg/www.thi...73213847a9.jpg

cars like these would come from japan in a high cube container
https://cimg2.ibsrv.net/gimg/www.thi...cd76a18e7e.jpg

Most came with damaged parts, the idea is to fix them up and have a nice car here from another country
https://cimg5.ibsrv.net/gimg/www.thi...f92b590019.jpg

I have modified and tuned many of course
https://cimg3.ibsrv.net/gimg/www.thi...34ea2539bd.jpg
RB26DETT twin turbo 2.6L engine with a six speed ^

https://cimg6.ibsrv.net/gimg/www.thi...344318cf2c.jpg
2002 Nissan GT-R R34 skyline single turbo going to Jamaica

I've got so many pictures it sickens me. But I can **** this thread full of gorgeous cars and tuning application/explanations if you want a run down of every single car
I bet if I try I can get over 100. Sorry I meant over 9000.

Re: BOV is opening under boost
 

Relax and have yourself a beer, it's Memorial Day for crying out loud.... :thumbsup:

- Rob

Re: BOV is opening under boost
 

oh good I was just coming back to say something like that. I'm glad we came to collective senses, good thinking

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Re: BOV is opening under boost
 

https://www.procharger.com/procharge...erlay-context= every blower company uses different specs for their kits but this gives you an idea what they use

Re: BOV is opening under boost
 

and my setup now I have a paxton making 6psi with no valve what so ever