I regret to inform everyone that my best E/T is still with the Paxton SN2000 and a 50 shot of nitrous:

12.043 @ 112.86 mph

Here is my best run from last night with the D1SC:

12.056 @ 116.62 mph

I am seeing 10-psig boost, BUT this is only at 5,200 rpm's (my tranny shift point). I have yet to manually shift at 6,200 rpm, where I normally take it to.

My ultimate goal is to run mid-11's. My next step is to replace my stock 19# injectors with 21# injectors, tweak my EPROM, then recalibrate my Superfueler. But I don't believe this will be enough to gain 0.5 seconds (opinions please). If I'm right, I'll have to go to the smaller blower pulley.

But for now, that elusive 12-flat barrier still exists....

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

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
Former Paxton (6-psig) with 50-hp nitrous: 12.043 @ 112.86 mph.
ATI D1SC (10-psig): 12.056 @ 116.62 mph.
Future ATI D1SC (?-psig): Gotta catch them pesky 26-psig boosted TTA's!!

http://willie.camaro-firebird.org/

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

[This message has been edited by Willie (edited July 07, 2001).]

 

Willie...you gained 4mph! Dont look so closely at the time, as many things can affect that, especially the humidity, heat, & altitude. Come run down here in PHX...you will be mid 11's for sure if you can hook it up.

How did your 60ft's compare on those runs? When you do shift at 6500, do you pull all the way? What was your finishline RPM? Changing your shift point (or manually shifting) can net you more than you think, if the motor is still pulling hard in the upper RPM range.

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Mike Metzler (Desert86Roc)[*] Check Out:SpeedWorldMotorplex.com[*] Check Out:Chevrolet F-Body Online Part & Illustration Manual[*] My 86 IROC 305 TPI Page (406 build in progress)

ET's @ 1250 ft[*] 14.28 @ 95.461 mph (uncorrected, NOS, no headers)[*] 15.362 @ 88.238 mph (uncorrected, headers, no NOS)
<><

 

I guess my question would be how do you get the boost up faster? change the blower pulley? if you are not getting to 10 lbs until 5200, how much power are you loosing (or not gaining, I guess is a better discriptor), by the boost not being there until 5200?

BW

 

Call me crazy but I can't believe you got 12.0's on factory injectors. Thats outstanding in my book. I saw big improvements when I went to 24#ers..

 

I agree. The weather conditions were much different between the two runs. My run with the Paxton/nitrous (last year) was in June (very hot and very dry). The run last week was during our monsoon season (84 degrees and 77 percent humidity).

Almost identical.

It's actually 6,200 and the answer is yes. I have evaluated different shift points from 5,000 up to 6,200 when I removed the Paxton but ran only the nitrous and my quickest times are at 6,200 rpm's.

The finishline rpm is in the high 5,000 range, depending on speed.

Yes. Faster and higher.

Boost is proportional to engine rpm, so it is never constant. The best I'm able to do is to use a high stall torque converter, so boost is built immediately. My Vigilante has a flash stall of ~3,800 rpm. I would never go higher on a daily-driven vehicle.

There is a common fallacy out there; that bigger injectors are always better. This is far from the truth. At a BSFC of 0.47 (a good value to use on modern fuel injected vehicles), a 19# injector can support 363.57 horses at 55 psig pressure. To support the same number of horses with a 24# injector, fuel pressure must be lowered to less than 40 psig, otherwise a rich condition will occur and low end driveability will suffer, even with a custom EPROM.

The advantage to running the Superfueler is that I can determine proper injector size at the low end of the rpm band, thereby keeping my low-end driveability. The Superfueler adds fuel only in boost that covers the high end.

The reason why I decided to step up to 21# injectors is to reduce my duty cycle, which now stands at over 100 percent. I feel 24# injectors are overkill on a 305.

Willie

 

Willie, that's not quite true. A 24# injector would actually be the better overall choice in your 364 HP example. At WOT 1) the injector duty cycle would be decreased, extending the life of the injector and 2)the required fuel pressure would be less than 55 psi, extending the life of your fuel pump. As long as you're running the proper injector constant in the PROM, low end driveability would be just fine. The BLM/INT functions will correct back to stoichiometric when not in PE mode.

24# injectors might be overkill on a stock 305, but not yours. 117 MPH through the traps in a 3700 lb car roughly equates to 475 HP. Since you're up over 250 HP from stock, think you might need a little more fuel?

If you want to size the injector for N/A operation and use the Superfueler to cover boost conditions I'd go with 23#.

If you want to keep the injector duty cycle less than 100% under boost you'll need at least 26# and maybe 30#. You could set up the fuel system so that the main injectors fuel the engine up to MAF saturation @ 255 g/s and have the Superfueler start to add fuel at the boost level present when the MAF saturates. Of course you'll need to change the injector constant in the PROM to retain non PE mode driveability. I think idle stability and low speed driveability will be just fine.

 

Mark,

What I find interesting is that whoever I talk with, they all have a different answer. I talked with Rich at Cruzin and he feels 21# injectors is the way go to.

A guy I know, Ryan, owns a '92 305 Formula. He installed a 10-psig Paxton and 24# injectors, along with a custom EPROM. He has told me that he has lost a slight amount of low-end response.

I have to base my decision to go with 21# injectors on what Rich told me and Ryan's experience. Then again, the 21# injectors are on order, so you've got time to convince me otherwise.......

Willie

 

Do you want to get rid of the FMU?

 

Sorry Dan, I ordered my D1SC kit without one.

Willie

 

LOL, I was sitting here scratching my head wondering how to heck you ran 117 mph before I remembered you are running the superfueler. How does that work?

 

The Superfueler contains a plate that is sandwiched between the throttle body and plenum (similar to a nitrous plate system). There are three injectors that are mounted on the plate and sits basically on top of the plenum. I'll e-mail you a pic if you want.

The three injectors are fired by a "peak and hold injector driver" module. The module is controlled via a dedicated MAP sensor through a "fuel curve generator" (FCG). The FCG is the size of a stereo equalizer and is fully adjustable. The low set point is first adjusted, then the high set point. There are ten separate adjustment points between the low and high points. Each adjustment point can be set to fire the injectors from zero to 100 percent pulse width.

When the engine attains the low set point boost level, the additional injectors start injecting; the volume determined by the FCG. The additional fuel needed is delivered by these three injectors, not by raising fuel pressure forcing more fuel through the eight "normal" injectors.

The Superfueler is a dedicated system that works outside the ECM parameters. Hope this answers your question.

Willie

 

Ultimately it's your car and you've got to be happy. If thats what you want to run, go for it. You know I'm running the 21#'s in my car and like them. BTW, custom EPROM can mean a lot of different things. I believe Ryan's loss of low end is not a function of the injector but rather the tuning.

 

In the end, I will be. But I'd like to get there with the proper size injector... the first time.

The problem is I do not know conclusively that 21#ers will work.

I won't go naming names here, but Ryan's EPROM was burned by someone close to this board.... and he knows his stuff. So I'm not sure what to make of Ryan's situation.

Willie

 

Good times Willie!A little more tuning you will be in the 11s.You gained about 4 mph which is a lot and your not even shifting out your car.You will most likly see more boost at 6200 maybe 2 of more lbs.I see you are going to bigger injectors.Can you just put in bigger injectors in the superfueler instead?I have never heard of 21lb injectors,who sells them.Why not a 350 22lb injector?Why not a 24 instead of a 21?Not much of a difference,and might support other small upgrades in the future.Just some suggestions.Let us know which path your taking.Good luck

 

like my uncle always told me,

"welcome to hot rodding "

good times btw willie

 

Right off the bat I have to agree with Desert86Roc, the 4 mph gain is a significant improvement that should result in better times. Environmental variables could be having an effect. I have, however, seen instances where MPH increases but E/T remains the same. Is there any significant difference in your 60' times? That could help evaluate whether you should be running faster or not with the MPH you're currently turning out. On top of that, revving the engine higher could give you the edge you need. Your MPH may still go up if you rev all the way up...

Are you running lean at WOT? I'm not sure if bigger injectors would do a whole lot for you if your fuel mixture is already suitable during your run.

Glad to hear the car is running strong at least!

Dave

 

congrats on yyour time. Please read my "Superfueler" post. I think I should probably run one, before i make my first runs w/ the blowers. butI have a few quesions. thanks

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SUPERCHARGED 87 GTA: Blk/Gld w/Superam, 355cid Trickflows, forged pistons 9.5:1. Auto 2,600 stall, 3.45 9 bolt disc, Best time & mph (Naturally Aspirated): 13.567 @ 101.900 w/ a poor 60ft. Best mph: 104.3 *This car is 100% NYS emissions legal, w/ all emissions controls!* "If you want to have a fast car, hang out w/ those who do!"
http:// www.community.webtv.net/munks87/JustinsGTApage.com
VORTECH S-TRIM, INSTALLATION IN PROGRESS: 10 & 15 LB> PULLEYS, CUSTOM HKS RACE BYPASS, CUSTOM DUCTING W/ COLD AIR, SWAPPING TO SERPENTINE, & MANY EXTRAS! BEST TIME: 11'S I GUESS. WE'LL SEE IN SPRING!

 

Willie, once you get that thing to hook up, your et's will be better - in proportion to the improved mph!!

------------------
Tim

1992 Z28, 305 TPI 5 speed, 12.1 sec @ 114.7 mph

1984 Berlinetta 305 TPI Auto, 13.8 sec @ 99.7 mph

 

Why exactly do you want larger injectors?
If you feel there is a demand for more fuel at wot why cant you get it out of the superfueler?
You said youwere going to have custom EPROM work done with the larger injectors... there is plenty of room in the lower map table for more fuel with the stock injectors.

Not picking up ET while increasing MPH could be related to a few things.
It does mean you are making more peak power, it also means you are not getting out of the hole / moving any better...probably worse.
Did you have worse 60' times? I expect you woudnt be asking if they were
much worse... they must be on par with the old 60' times.
I'm no NOS expert but I've heard that those cars will run the same et as a boosted car at a lower mph.
The D-1's power band... I'm betting the D1 make less power on bottom than
your old supercharger/nos combo? With the 700r4 and its big gap in the 1-2 shift, a loss of power like this could really bring out the low end power difference between the ATI and than the paxton nos combo because you can see the difference twice... once at launch and again when you hit second. If this is the case, the key is getting it into the power band quickly and not short sifting it so that it recovers better into the next gear... a higher stall converter maybe?

As for your shift rpm problem... B&M makes a governor spring kit that you can install yourself. I did mine when it was out of the car (did the speedo gear and converter at the same time) I don't remember anything that was hard about it. Its like changing the mechanical advance in a distributor. The worst part is you might have to take it apart several times to get the right weight-spring combo to get the right shift RPM. Use your dyno sheet to work out your best
shift points. I wouldn't be surpassed if they were higher than what the paxton/nos combo wanted.

 

Here is my stab at injectors-factory injectors are set up to give a very linear smooth progressive fuel map thus giving a car good idle and no hesitation.Larger aftermarket injectors require much more than a 10 minute chip burn to give the same results.So I would like to ask you what kind scan tool do you have so that you can properly produce good results with your new combo's?