Just started tuning WOT with the EBL. Running a D1SC with a 4" pulley that should be good for about 8-9 psi. However, everything starts off well, it makes boost about 4 psi around 4200-4800 rpms then it just dies off. At 5500, according to the datalog, the boost is at 0 psi. I thought it could have been spark plug gap and the BOV (Procharger Red Race Open valve) so I check the gap and reset them to .032 from .035 and checked the nut on the BOV which was loose and tightened it back up with 1/8" of the screw sticking out over the nut per yellowbullet.com instructions of adjustment. Did another run on a 10 degree hotter and it made 4.5psi from 4200-4800 and then .5 psi above 5k rpms this time. Once it shifts, the boost comes back to 4.5 psi and all is well again until around 5k rpms. The boost flat lines and then looses all boost. A/F ratio was 10-10.5 so rich and I'll lean it out some but not too much before I fix this issue.

Now, that you have the background, here is question. I have a cold air box that I built. It has two 90* bends off the inlet side of the supercharger routing it to the front grill. The box has one hole behind the headlight for fresh air. My thinking, the Procharger is running out of air thus flat lining and loosing boost above 5k rpms as it demands more air.

Could I be right on my thought process before I try just putting the filter on the end of the inlet and making a test run?

 

Can you throw up the datalog? Only possibilities that I can think of is either your engine flows that good and makes enough power on its' own at that RPM, wrong pulley size, boost leak somewhere, or is a tuning issue.

 

What engine is this on?

 

Make a pull with no filter. If that doesnt help, it sounds like belt slip. Or, could valve float cause this? Im thinking it could.....

 

I thought boost leak as well but everything is tight and nothing seems to be leaking air that I can see.

This is on a 383 with 195cc AFR Eliminator heads, GM847 cam, 1.6 rockers, AFR 8019 springs, Victor Jr intake with a 1550, 60 lb/hr injectors (64-67% duty cycle right now), 8 rib setup, no belt dust detected, no knock retard detected at WOT, spark plugs look good besides being a bit rich. Airflow is maxed at 255 according to the datalog. Recently, just put on the DynaMod ignition module from DUI to replace the 369 module. The truck pulls great from 4000-4800 then just falls flat on it's face. I may put the old 369 module back on and see if that fixes the issue but don't think that would explain the loss of boost.

I don't think valve float as I'm running AFR 8019 springs which have only 1300 miles on them at most.

 

Running a Goodyear Gatorback belt. Belt is tight and rubbed my finger on the inside of the belt and my finger was clean so I think belt slip is not the issue but I did check for that.

 

Have you had it on a dyno? Something strange about valve float...... our local group has had a few episodes of it, and for some reason it always happens at 5k rpms. On the dyno sheet it will look like a nice steady pull up to 5k and then boom falls off a cliff. A boost leak im thinking should just flatline the boost pressure, not drop it. Would be cool if there was a way to log your blower pulley rpm during a pull....

 

Yeah, if the open filter doesn't work, then I would suspect valve float next as that's all it can be at that point I would think.

 

Not necessarily. Depending on the camshaft's LSA/overlap, the pressurized boost can be blowing right out into the exhaust just before quench. Can you post a datalog?

 

I wouldnt think the cam profile would ever cause it to fall on its face suddenly at 5k though....? Or drop boost suddenly.... should be steady over the rpm range I would think.

 

Hard to say. That GM847 cam he is running is pretty nasty, if he is running a 4" pulley rated for 8-9 psi on a stock engine at a given RPM, and his engine is more than likely making a lot of power from the getgo, then his boost will be much lower than advertised. That GM847 cam is not really designed for supercharged applications, he may need a bigger pulley or a bigger supercharger to keep up with the engine if it's breathing that well to begin with. A datalog will tell the real story though...

 

The installed height could be wrong causing valve float. This would hang the valves open longer and possibly dump the boost out the exhaust. Thats my thought so far. If no leaks, slip, or restricted filter/inlet. Wrong cam would mean low boost across the board. -I think.

 

I would check the filter, by running an open Supercharger and seeing if the boost comes back.

My other experience with this is a leak in a line somewhere you can't easily see(crack in tube, tear in coupler, kinked coupler somewhere).

Last make sure under boost(but at only 5 psi, I don't think it would be an issue) to see if you have a silicone hose folding in under boost.

 

I doubt its valve float. I been there and never dropped boost. I wrecked my guides so bad pull would stop at 5500, but still had boost. Just acts like a rev limiter.

A coupler sucking in on intake side of blower could kill power or also act like a rev limiter. But still should see some boost.

8019 spring installed correctly will not be seeing float at that rpm on that cam.

Try buying or borrowing a pressure tester to go on the cold side piping and hook up to a air compressor and hit it with pressure to see if you find anything.

 

I agree. I doubt its a mechanical issue. Its got to be in the intake tract somewhere(or the blower stops turning!

Also, is the BOV losing signal and opening?

 

Ok, I can't figure out how to post the EBL log which is a .dat file. So, I can email it if someone wants to look at it?

Thanks!

 

PM it to me...

 

I can send you an email with it...I can't figure out how to post the .dat file.

Thanks!
N/A - it would pull to 6400-6500 no problems. 6200-6300 was the sweet spot on a shift point though.
I was running a 4.25 pulley before this and saw 4 psi as well with that pulley. With the 4.00, still seeing 4psi but goes down to 0 or .5.....just like it starts to tamper off.
I know of others using a similar designed cam without issue so don't think that would cause the boost to tamper off and disappear completely. Lose some of it yes but not all of it.
Couplers are new, less than 4 months old. Intercooler is a treadstone TR1045.
I'll check that and see if I can find one of those. 8019s were installed to the same height as the 8017s which I found to be installed to the same height.
BOV is blowing off once out of the throttle.

 

PM sent

 

Just got it, sent one back to ya...

 

Check email for datalog!

Thanks!

 

K I am looking at it now.

The datalog starts 4:00 minutes it. Give me a little bit to see...

 

Idle SA is good at 36*, but I see it dropping down to 22* without any boost pressure so far when blipping the throttle, can you post a picture of your SA Main Table? O2's look good at idle, but at 4-5 psi of boost pressure they still average stoich (450mv) for some reason, it doesn't increase, neither does your injector duty cycle. Let me keep watching, hold on...

EDit: When I say Idle SA is good at 36*, I mean total timing. When you start building boost though, it immediately drops to 22* when you should be pulling 1* for every pound of boost to no lower than 19*. At 22* SA boost pressure should be closer to 15-psi, yours is reading 22* at 1-psi, 1-psi should still be close to your total of 36*...

 

Analysis is showing a much better description of it, as for some reason the WUD is not being accurate. Analysis screen does show your injector duty cycle rising, but your O2's remain stoich, are you running an Open Loop tune? I switched the WUD to wideband setting but I don't see your air/fuel. If your running a wideband where is the reported data as the BLM and INT are locked as are O2's, and I can't see your fueling...

 

WB should be on the right for A/F ratio. It shows it on mine. On the WUD, its in the right as well. This is an open loop tune. Pulling timing out to 22-24 degrees so it'll be safe while I try to fix this issue. Was 25-26.

 

Lol i bet that car would take 32-34 deg on 4 psi. But thats after you figure this out

 

Compression is high for a boosted engine so probably 26-28 degrees when its all said and done I think at 8 psi. I kept some compression in it for torque in a truck while not in boost since it is a truck with more weight than a Camaro or Firebird.

 

Yeah that may be about right. Thought you had non eliminator190's. the 195 elims may like the 1 deg per psi rule. Mine did

 

Checked all clamps, they were tight, check the firmness of the hoses, all are good as well.

 

My WUD is P4 based, if yours isn't then that is more than likely the issue why I can't see some key things. Your spark advance is an issue though, can you post up a screen capture of the SA Main Table, your VE tables (not the extended one), and your BST table? I would also send RBob a copy of the bin file for him to examine, because my XDF is different if your not running EBL-P4. If you have P4, then send me the bin, I will make some changes, and you can test it...

 

I also have the P4. Bought it May/June of this year. I'll throw some spark tables up. Again, it's about 4-5 degrees low due to me just trying to get everything worked out. I've never seen low timing mess with boost as cause a massive decrease.

 

No need to throw up the tables then, just send me the bin...

 

Spark and Fuel tables

 

Email sent Street Lethal

 

Got it, looking at it now...

 

Your timing is escalating the wrong way, which is why I mentioned earlier that it shoots down to 22* when you reach 1-psi of boost pressure. If you look at the row of cells going downward in the 100-kpa column, your timing is off by 10-12 degrees at times. You have to invert the table so that the data going downward in the 20kpa column reflects on the 100kpa column, and vice versa, with the middle ones being changed as well. If you'd like me to do it for you, as well as a few other changes, let me know...

 

Yeah, this was actually a tune I got from someone on here as a start file and I've never looked at those tables.

That would be great!

Thanks!

 

I just looked at the BST-Spark Retard table, it looks very good as it is. With a total of 36* in the SA Main Table, the BST retard table is pulling 8 up to no more than 12 degrees after your total timing comes in and when your in boost, which is good. I am not going to touch it though, as you need to see where your boost is at that point first, and then add or reduce timing in that BST table based on 1 degree for every pound of boost pressure wherever needed. Your Max-SA table is reading 41 for some reason, I'm going to bring that down to 36-38. I'll have it done in a little bit...

 

Whats the air fuel do at the boost drop rpm?

 

With the corrected SA table, it should run better, however, would that cure the boost issue that post-igniting the fuel/air and loosing the boost out the exhaust valve?

Is that the theory here?

 

In boost, it's about 9.9-10.5 and when it drops, it goes from 10 to 11 just up and down.

I know it's rich...been making small correction to get it back to 11:1 so at least it'll be at a better position until I fix this boost issue.

 

Could it be too rich its blowing spark out? Does it continue to pull past 5000 just noboost? Or does it lay over and stop?

 

It continues to increase rpms, just doesn't have the power then it does under 5k and loses boost...kinda tapers off. Once it shifts, power comes back on and 5 psi comes back instantly.

 

I think a float would show more variance in air fuel.

Timing even 10 deg off will NOT bleed off boost. Been there tested that. So that aint a concern. Just room for improvement.

I would look at belt slip again and leaks.

 

Yes, centrifugal boost is based on a set RPM. The spark advance as it was would give you the same effect as valve float, essentially hitting a brick wall and holding back. I adjusted the Max-SA to no more than 38 degrees, I inverted the SA Main and Extended tables to reflect correctly, so now you will see full timing build fast and come in at just under 3000-RPM, and no more than 36 degrees at 100-kpa. The BST-SA Retard table will pull timing in conjunction with boost, but I didn't touch that because we don't know your true boost pressure just yet. The SA Main Table needed smoothing, because your Inital-SA is at 22 degrees like mine, but sometimes dipped below that. You should have a much smoother idle now too. Base timing (spark reference) is still at 8 degrees, I didn't touch that, but I would recommend bringing that to 12 degrees and matching the balancer by hand to 12 degrees as well later on, your starter will thank you...

Email sent

Edit: don't forget to do some VE Learns, the timing change will need that...

 

Very cool stuff stuff, and what a guy (SL) for taking the time.

 

I'll try it out tomorrow as well as the filter is on the flange of the supercharger.

Thanks for the help...looking at the tune now.

 

It was definitely the tuning in the original bin that you sent me, and I will explain why. With your Spark Advance escalating the wrong way, you were reading 22* of timing at your Idle RPM, then it immediately jumped to 36* of timing way before 2000-RPM upon light throttle, and as you get into the throttle with RPM's increasing above 2000-RPM, your Spark Advance was now going down when it should have been going up. In the analysis, one pound of boost pressure was prevalent at 2900-RPM, and your Spark Advance was now down to 24*, it got as high as 4-psi of boost pressure at 3600-RPM, and the Spark Advance was now down to 22*. The reason why you lost boost above 4800-RPM is because of your extended Spark Advance tables which control 4800-RPM and up, as these essentially looked untouched and shows why when you reached that RPM it fell completely flat on its' face. You had just enough Spark Advance for 1 to 5-psi of boost pressure, but once 6-psi would have been reached there was just too much timing being pulled out for the engine to keep up with the load, so you were only meeting your engine halfway from a timing perspective. Remember that we tune our BST Spark Retard table based on the final value in the Main Spark Advance 100-kpa column, and the final value of your Main SA table's 100-kpa column should be 36* after 3000-RPM and up to 4800-RPM, and 36* from 4800-RPM up to 6400-RPM in the Extended SA table, but yours was 28* in the 100-kpa column, with the BST table now pulling up to an additional 10 degrees from that 28* before 6-psi of boost pressure was even reached...

 

but... if the engine is still accelerating past 5k, then the blower should be spinning faster and making more boost. (unless its maxed out)
im still stuck on some sort of leak, restriction on the inlet, or belt slip. doing the test suggested above of pressurizing your charge piping from the blower to the throttlebody would be a good one to perform. pump it up to 20psi or so and see if it holds/spray piping with soapy water. also make sure your bypass valve isnt malfunctioning.

 

Watch his airflow at 135kpa (5.07-psi), and watch what happens to it afterward as his boost pressure goes down, and as the RPM keeps increasing. Air flow gets locked at 255 all the way to 5350-RPM (no higher, he let go after that) and at that point boost is only at 1.5psi. Overall, the change in Spark Advance will improve his performance, but if it doesn't help his boost pressure issue then it seems as if the supercharger cannot keep up after 5-psi. The analysis below has the data slightly different than what I posted because he hit 5-psi a few times, and in different gears, and the cells will reflect that. Please note that I set the WB to the TT-1 setting in the WUD and was able to retrieve the fueling data, not sure why my original WB setting wasn't working. But it's there now regardless...