Ok, I spoke to Willie on the phone about this and he was very helpful.

I have a Paxton 10lb blower with a Bosch inline fuel pump. I'll be using my stock 19# injectors.

What about increasing the pulse width of my injectors, running around 48#s of fuel pressure, and running 30* timing?
does that sound like a 12 second receipe? Or a mess.

------------------
91 Formula
305 TPI 5speed
1LE/G92/WS6
w/GTA gfx,rims,hood

Paxton-charged,Cold air ind. w/K&N, SLP airfoil, ported/polished plenum, March pulleys, Crane AFPR(43psi),Crane Gold 1.6rrs,MSD coil,MSD6AL, Holley 9mm wires, fastchip, Bosch O2sensor, SLP headers & catback,short shifter,3:73s w/Auburn posi,160* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.

 

You need to run 24 lb injectors with that combo.

------------------
87 Formula
406
AFR 210
miniram
vortech t-trim
55# injectors
DFI
th400 8"converter
moser 9" 3.73
convo pros

www.homepages.go.com/~thess406/Blown406Bird

 

Ryan,

As I mentioned on the phone, the following is my combination that's yielded very nice results:

6 psig boost +
Stock 19# injectors +
16mS+ pulse width +
50 psig fuel pressure (no vacuum) which increases to ~55 psig under boost =
950mV O2 (still too rich based on puffs of black smoke)

YOU DO NOT NEED LARGER INJECTORS. If you do, you will have to decrease fuel pressure to compensate -- and you don't want to do that. Proper PROM parameters will yield much better results than just throwing in larger injectors. Larger injectors seems to be a common fix. It is not. It is a fallacy that seems to be very prevalent.

Putting it another way, I have run a best of 12.57 with only 6 psig boost. My plans call for running sub-12's with 10-12 psig boost WITH my stock 19# injectors and NO FMU. To date, I have revved my D1SC to 8 psig boost at 60 psig fuel pressure which yields 900mV O2 readings -- just about perfect. Now, if the track would just open back up.....

------------------
Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
12.57 @ 111 mph.
12.04 @ 114 mph (50-hp nitrous).
http://members.optushome.com/au/downunder1/rides/willie/willie.html

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

 

True, you dont need to replace the stock injectors if you only want to run 6psi, but if I spend over 3k on a supercharger, I'm going to go for at least 10psi, at which point even though the stock injectors will still suffice, performance will still suffer. Everybody i the know knows that the stock GM injectors are crap and lock down before they should. I'm not trying to flame or be flamed here, but for $250 on top of my new 10# paxton, I'd get a set of SVO injectors, and you'd be really suprised how much better your performance will improve over stock injectors. I plan on getting a Procharger D-1 pullied for 10# (big @$$ pully) with a three core intercooler and SVO injectors soon, as I have seen dyno pulls of other thirdgens with P600B's at 9# with the SVO injectors....man! these cars really wake up when you give 'em a little positive manifold pressure!! I'll post pics and dyno slips as soon as I get everything going.

------------------
1990 Firebird Formula 350 speed density TPI; K&N, air foil, throttlebody coolant bypass, underdrive pullies, MSD 6AL, MSD HEI coil, 8.8mm wires, adjustable fuel pressure regulator, Hypertech Thermomaster chip, 160* thermostat, fan switch, B&M stage 2 shift kit, Edelbrock 1&5/8 headers, gutted dual cats, Flowmaster 80 series muffler, 3.73 posi rear end

 

P.S - Larger injectors are NOT a band-aid or a quick fix for SC'd engines. It is a fact that when more air enters an engine, more fuel is required to obtain the proper fuel ratio. I can see how only 6psi might get by with a simple PROM calibration, but the stock injectors can only take so much...for that matter, any injector can only take so much before you risk burning them out or whatever other horrors you may encounter from exceeding the limits of an injector. If all you rely on is a PROM, eventually you'll burn a piston because your injectors crapped out and made you way lean....$250 for a set of injectors doesn't sound so bad now, does it?

 

Let me address every point MelloYello makes.

Unfortunately, you do not know the entire story relating to my experience with my car. I WAS running 10.5 psig boost with no lean out condition. I also have a linear 21-LED O2 bargraph in my car and I know the status of my O2 millivoltage at any given time. Suffice it to say, I was still running extremely rich -- over 1000 mV.

Are "stock" GM injectors the same as Bosch injectors? I believe GM uses both Bosch and Rochester, but could be mistaken. And indeed they do lock down, but only at very high pressures, not due to flow rating.

This site is 100 percent tech. There is no such thing as flaming others here. All we do is state what we perceive to be opinion or fact. I appreciate your input because it raises many questions that should be addressed. My opinions are not based on conjecture or something I've heard through the grapevine. They are my personal experiences with supercharging which started over three years ago.

I just installed my D1SC with three-core IC. It replaced my Paxton. So far, I've been able to attain 8 psig boost with a total of 38 degrees timing. At this point, my fuel pressure has increased from a no-vacuum setting of 50 psig to 60 psig and the result is 900mV O2 readings with 19# Bosch injectors. Perfect, in my opinion.

Agreed as stated in my original reply.

Typically, an injector will burn out prematurely when too much fuel pressure is used. I might be wrong here, but I don't think you'll have premature failure by holding it open longer (pulse width).

You will only burn a piston if and only if a lean condition occurs. It has nothing to do with flow rating. I still contend that larger injectors are not necessary based on the fact that I was running 10.5 psig boost with my old Paxton. Why spend $$$ if you don't have to? I have yet to blow my engine in over three years of supercharging with 19# injectors.

Bottom line: Make sure you're running 900 to 950 mV on the O2 readout at WOT through the entire rpm range in a higher gear (i.e. second or third). If it's less, bump up the pressure instead of replacing the injectors with higher flowing units. You will get the same end result AND retain more driveability when NOT in boost.

Willie



[This message has been edited by Willie (edited January 29, 2001).]

 

Increacing pulse width does in fact reduce injector longevity, and can also rob you of power. The higher the duty cycle (as a percentage), the more stress imposed on the injector, and along with it is the increased likeleyhood for failure due to sheer stress and overheating. Also, power can be lost in high duty cycles because the fuel simply takes too much time to be released...sure, all the fuel might still be all combusted, but not at the most oppurtune time. Also, I noticed on you web site that you use water injection on the street and disable the knock sensor for the track. This makes me wonder if you produced the numbers in your signature with race fuel. If you're engine makes significantly less power on the street than on the track, I could see how you're combo has lasted for three years. In my posts, I was referring to combos diven on the street, sorry for the confusion, but I like practicallity.

 

Thanks for the info. I know 80 - 85 percent duty cycle is maximum, but what I don't know is whether this value is calibrated into the PROM. What determines duty cycle? And can we calculate what it is?

I've experimented with water injection at the track. On the street, it stays armed. At the track I can run 38 total degrees with the water injection turned on at 3 psig boost. Without water, I have to retard my timing to 34 total degrees to prevent detonation.

As for the knock sensor, disabling it does not seem to improve E/T's, so I really don't use it any more.

In a nutshell, I have never used race fuel or any octane booster, only 92 octane unleaded fuel. I feel that I only produce a slightly more power at the track than on the street, thanks to my track exhaust, nothing else. With this true dual setup, I need to increase my fuel pressure by 2 psig to retain >900mV O2 readings. That to me indicates that my engine breaths better with this exhaust. But I never run this exhaust on the street (except to and from the track). It's way too loud and loses too much ground clearance. On my dyno runs, I did use my track exhaust. I hope I've cleared up any misconceptions here.

I should also say that some info on the webpage is incorrect. It reads 12.04 @ 112.9 with 9 psig boost. It should read 12.04 @ 112.9 with 6 psig boost and a 50 shot of nitrous. My best with 6 psig boost and no nitrous is a 12.57.

I hope I've cleared up any skepticism. In addition, I can tell you that I drive my car daily (for business too) but I do NOT street race. In fact, it's useless racing on street tires. So it's a waste of time and energy (and rubber!!). I use Hoosier Quick Time DOT's at the track.

Understood. Thanks for clearing it up.

If there is still any doubt in your mind, contact Dirk Timmermann (founder and administrator of this site) or Tim Burgess (Electronics board moderator). Both are good friends of mine and both live here in Tucson. I believe they will confirm everything I've stated to be fact.

Willie

[This message has been edited by Willie (edited January 29, 2001).]

 

We've exchanged some interesting ideas and brought up some interesting questions in this topic, Willie, and I'm sure whoever has read these series of posts has learned a great deal. I have a few more comments, however: a 12.57 with 6psi is quite plausible, as you have demonstrated, with the stock injectors. My argument was based on your time of 12.04 with 10psi. Now that I know that you ran that time with 6psi and 50hp shot of nitrous, I can see how your numbers were accomplished. Let me add that 150hp shots of nitrous are used on stock TPI's (including stock injectors) because the fuel jet in the nitrous system draws its fuel directly from the fuel pump via schrader valve on the fuel rails, therefore eliminating the need for any more flow from the injectors. Willie, your car is awesome, and I applaud your efforts towards its evoloution. Soon, I hope to become your brother in the world of D-1 intercooled boost.
P.S. - I will try to find how to alter pulse width as a function of the PROM....If I get any info on the matter, I'll post it for you.

Cheers
Kyle

------------------
1990 Firebird Formula 350 speed density TPI; K&N, air foil, throttlebody coolant bypass, underdrive pullies, MSD 6AL, MSD HEI coil, 8.8mm wires, adjustable fuel pressure regulator, Hypertech Thermomaster chip, 160* thermostat, fan switch, B&M stage 2 shift kit, Edelbrock 1&5/8 headers, gutted dual cats, Flowmaster 80 series muffler, 3.73 posi rear end

 

Don't ya just love this board!!! This is what it's all about, sharing knowledge and learning from each other.... I readily admit I do not know everything -- that life itself is a learning experience from beginning to end -- that I'll always be open to new ideas.

Now I understand why you were skeptical. I like to video my runs and have most of them on tape, including all three of my best runs:

1) 6 psig boost = 12.57
2) 90-hp nitrous only = 12.58
3) 6 psig boost + 50-hp nitrous = 12.04

I don't recall who I ran against in #1, but I was paired up with a 2000 Camaro SS in #2 (beat him by 0.9 seconds), and a first gen Camaro in #3 (beat him by almost two seconds).

Now that my Paxton and nitrous are history, it will be truly interesting to see how my car performs with the D1SC.

I like to experiment at the track by changing ONE THING. That gives me a true evaluation of that ONE THING. Unfortunately, I had a couple of issues on my 12.04 run. I fried my Auburn on my previous outing to the track and was unable to do burnouts. Also, it was on this run that I fried my 3-4 clutch in my 700R4. Somehow, I made it to the finish in record time. Had everything been working, maybe I could have run a sub-12 second 1/4. I now use a Torsen unit and have a ton of mods to the transmission, including a five-disc Vigilante which will allow me to manually lock up my converter without worries of premature failure.

Thanks for the compliment and thanks especially to Larry and Darrin who have helped a ton installing the ATI kit with relative ease -- because the directions suck!! According to ATI, only four third gens have the D1SC kit and three of us know each other, thanks to this board!!! When it comes time for your install, please let us know and we'll help as much as possible.

And so far, I'm very impressed with the performance gain from the D1SC. Up until a couple of weeks ago, my goal was to run an 12 flat (don't want to install a roll cage in my daily driver). But on my last outing to the track, I watched a Turbo T/A run an 11.59 with 26 psig boost!!! So now, my goal is........ we'll see.

Excellent. It would also be interesting to know what absolute maximum pulse width is because I'd like to know if I'm exceeding 85 percent duty cycle @ 16mS.

Willie

[This message has been edited by Willie (edited January 30, 2001).]

 

You said you have three runs on videotape, 'eh? It would be cool if you could post them on your website, as I think there can be alot learned from just watching a run (plus, it would help ease the pain of no track time during the winter )

Thanks Again

Kyle

 

Not to interupt this interesting debate, but the whole question of "duty cycle" gets muddied up when you consider injector pulse width and rpms (which are often overlooked).

I've asked this question before on the Prom Board as to how is the injector pulse width measured...per revolution or operating cycle (two revolutions). I was told that on our ecms that it is per revolution. Thus when an injector is open for 10 ms, it is 10 ms during the revolution of the engine.

Now this becomes important as the revs increase, as you have less and less time as the rpms increase. At 6,000 rpm, you are making 100 revolutions every second or 10 ms. Thus even though your pulse width may SAY 11 or 12 ms, you have only 10 ms to get your injectors to deliver enough fuel during that revolution. At 10 ms (or higher) your injectors never close @ 6,000 rpm.

At 3,000 rpm you have twice as long, and thus can keep your injectors open upto 20 ms, at 9,000 rpm (just another example, not a realistic rpm) you only have 6.667 ms to fire your injectors.

As I said, this is based on the concept that the injectors pulse width is based on a "per revolution" basis. This question was answered by Grumpy, who I believe that if anyone should know, he would.

Sorry for the interuption, please continue.

 

Hi Willie.I am now still waiting for Fed EX to pick up my package.They are holding Larrys bracket also because the machine that does the mods to the bracket takes time to set up so they will wait for the 2 brackets to save time.Enough about this though.I want to know what you think of the power of the D1 compared to the Paxton.Are you confident you will see 11s ,with traction of course,with no nos?I saw a post you talked abou the intercooler.I too observed how cold the intercooler and inlet piping got after some driving.I caint wait to see the difference in heat(hand test)on the housing of the blower.I remember the P600B got hot,but not as hot as my friends Sn-93 Paxton did.I wonder what ATI's fluids composition actually is?After driving how confident do you feel that you are 11sec(or Faster)material?Like I said before to you,I wanted so bad for my friend to go the 305 route,I wanted to see the results of a full blower buildup of this cube motor.Im excited for you,keep us informed.One last one,what do think overall of the ATI blowers?Live up to the hype or what?I loved my P600B,but the oil line crap and hole in my pan was the only thing I didnt like.Im so siked.I willl send you my pictures Willie as soon as I get my custom crank pully from ASP in TX,im looking at about a month.I needed it custom made because of the crank trigger.I cant mount the blower belt because I sent him the factory crank pully for reference,plus I had to fork over $175 just for the one off pully.Have a great day guys

 

Wow Darren, that's a ton of questions.... here goes...>>

I can only guess at this time. It's been about six months since I had my Paxton, so I've gotten used to my car without a supercharger. So it's tough to say.

My plan has always been to break 12-flat. It was obvious the Paxton couldn't achieve this. That's why I decided to add nitrous. Now my goal is to produce more boost with the ATI. I've already removed the nitrous and sold it, so I think this speaks for itself.

Traction is not an issue. I run Hoosier Quick Time DOT's at the track and once I've heated them up, they grab like gum on hot pavement.

Yeah, ain't it great?

I can tell the blower itself will get hot -- it's only in the 50's outside now and it does get hot. I can imagine it will be much hotter when the weather warms up. But like you say, I couldn't even touch my Paxton, it was so hot.

It's proprietary. That means it's a company secret. We'll never know.

I can say that the D1SC builds more boost faster than the Paxton. But track and dyno results will confirm this, neither of which I have done.

Will do. I don't think I know -- is your car a 305 also?

Once I got it installed (thanks to you and Larry), I now look at it and realize how excellent my engine compartment looks now!! It looks so integrated that it almost looks factory. In fact, I had a plumber in my garage yesterday looking at my hot water heater. I just "happened" to have my hood up (imagine that!). He saw my engine and asked, "Is it stock?" HA!!! Except for the chromed/polished pieces, nothing looks add on. I'm impressed!!

As for performance, I am confident I made the right choice by going with ATI. The coming months at the track will verify/deny this.

Before ATI released the self-contained blower, I had decided to go with Vortech. Then it was released. I changed my mind in a heartbeat and have not looked back.

I can't wait to see your car. From the way you describe it, it's my car's cousin!!

Willie

[This message has been edited by Willie (edited January 31, 2001).]