1quikzz

So now that the race season is done for the year (for me anyway, due to snow) its time to re-evaluate and plan to get quicker. This year I put together a 87 buick regal with an L33 opened gaps, trickflow cam 216/220, lq4 heads milled .20, studded, t4 78/75 turbo intercooled no meth (yet) running 16psi. Rebuilt 4l80e w/shift kit circle d 3200 stall, trick chassis swapped 8.8 ford 3.55 posi. With all tubular adjustable arms, 90/10 fronts 50/50 rear shocks, cross brace welded into the rear frame. 28x10.50 m/t et streets. Car is a full steel body and full street trim. Times were deadly consistant this year at 11.90 at 118mph with a 1.86 60'. Leaving off the footbrake at 3k the car spins bad out of the hole. Im kinda dissapointed because I feel like the car should be much quicker . Any advice where I should go next? I feel as tho it has 10 second potential but something in the combo is just "off"

Hardtop Brian

I'd look at adjustable rear shocks. I went 1.52 60' with bolt on power on a 8.5 radial tire (used mx235 class tire) and strange single adjustable shocks in the rear, bilsteins up front. Set your tire pressure (I stay around 16/17 psi with a radial) and play with the shock settings until you find something that works.

Jake99

iTrader: (2)

Need to hook up first, try a Hoosier full slick to start, who tuned it? Seems down on power, had a car running 12.6 all day on a turbo ls1 8psi, just put a good tune on it and went 11.2@124. Also good fuel, e85 with 20 degrees timing will wake it up

1quikzz

I thought the et streets were a good tire, maybe I'm not boiling them enough before the launch? I tuned the car myself, (my first boosted tune) with help from sloppy/denmah's base tune. Its running out to 15 degrees at 16 psi on 93 octane pumpgas, E85 isnt an option up here. I didnt want to up the timing that much more untill I put the meth on it.

Jake99

iTrader: (2)

Do you have a radial or bias tire? Seems like the full hoosier slick does the best on a bad track, which im guessing is a big part of the problem. However even with .2 quicker on the 60 foot your still only at a 11.5 et, so your also down a lot on power. have you run the numbers to see where cr ratio is at? 16psi on pump gas id hate to tell you to try any more timing. What we do is run the timing as though it was a n/a motor, then just start pulling timing with boost, 28 at 0 then pull a degree per psi of boost till you hit 12psi at 16 degrees then lock in the timing at 16 after that. Seems to give the best spool up that was. Also are you logging your runs to make sure the timimg and a/f is truly there? And have you logged the iat?

Doug G

I get my best 60's launching just off idle and flashing the converter.
I would also go around the water box, do a quick 2-3 second spin, and line up.
MT Drag Radials 275/60/15's at 18-20psi, 90/10front, 50/50rear, 3420# with me in it.

1quikzz

Bias ply, they are the mickey thompson et streets. Im starting to think maybe I am off in the tune or just flat out down on power. The engine is a L33 so aluminum block and flat top pistons but has 317's milled so I have it at somewhere around 9.25:1. The timing is almost bang on what you suggested, 26 degrees at 0 then tapers down in the boost region to max of 16psi. I have a wideband in the downpipe and it hits clean at 10.8-11.3 (which I feel is pretty safe). The car "feels" fast especially on the street, the power hits like a freight train, it just isn't on the track lol. If you wanna have a peak at the tune, I can send it to you. Maybe I'm missing something.

murphinator

iTrader: (2)

In the past on another platform I also ran in the 10.9-11.2 afr range and it worked best for me but that was on a eaton sc with no intercooler and I was able to get the most timing in it with it that rich but overall I think your going to hear that your leaving a bit of power on the table with your conservative afr , if you up it to 11.3-11.6 do you have to pull timing to stay out of KR ?

I have never had a turbo car but building boost at the tree seems to be a main objective for those guys to et well of course that takes suspension and tires that can take that launch. What type of boost are you able to build at the tree without blowing off the tires on launch ?

poorhousenext

Some questions.

What is the curb weight of the car now with the changes you've made?

"GM's curb weight for it with std equipment is listed as 3164 Lbs."

What is the RWHP?

What do you weigh, as that adds to what total Weight to HP ratio of car?

What is trans shift RPM set at?

What is your tire dia?

What is your 8th mile speed and time. Using a Gear Ratio Speed Calculator at what mile per hour does car shift from 2nd gear to 3rd gear 1:1 ratio.

Would you be better off to use a 3.70 ratio, as I'm guessing trans is shifting from 2nd to 3rd gear at or shortly after 1/8 mile mark, thus losing any gear multiplication to help the engine pull the cars weight last 1/8 mile or so, an also to get it's weight moving.

It comes down to HP to Weight or Weight to HP.

Gearing change to help engine pull the car's weight could have effect of helping ET.

1quikzz

The welding/4l80e and 8.8 probably added 150 pounds, im 200lbs so im guessing a race weight somewhere around 3600lbs.

RWHP i dont know yet, I will get the car on a dyno come spring.

Shift point is commanded at 6000rpm usually a little delayed maybe 6100-6200rpm.

Tire is 28x10.50 16 on wagon wheel steelies.

Best 1/8 et was 7.67

poorhousenext

What's missing right now, is you don't know where you at HP/Tune, Weight, chassis setup, maybe even shift point wise if engine will allow you to shift at higher RPM than 6000 so you can shift closer to RPM engine makes it peak HP at, to get more use out of 1st & 2nd gear ratios to help move the weight of car, before trans shifts into 1:1 3.55 gear ratio.

Just using below calculator and 1/8 MPH, trans is shifting into "D" at are right after the 1/8 mile mark. From 1/8 mark to 1/4 mark looks like engine has only pulled back to around 5000 RPM from last shift. Using the below RPM Drop Percentage of 32.43% for 3rd gear = around 1946 RPM lost.

4l80/85
2.48
1.48 -- 59.68% (high) RPM Retention 40.32% RPM DROP
1.00 -- 67.57% (high) RPM Retention 32.43% RPM DROP

http://www.apexgarage.com/tech/gear_ratios.shtml

Your Time Slip looks a lot like mine, ET/MPH/60' wise. RWHP is 360/Mustang Dyno, 409/Dynojet. GM crate engine rated at 480HP at 5800 RPM. This is with 300 Tread wear street tires, no DR's or Slicks and 3.55 Rear gear. Due to 52% of car's weight being on rear tires I can't even spin tires off line.

Car's HP to Weight ratio is 9.97 LBs per HP with me in it an around 4 gallons of fuel.







I'm building a car now that I hope can run in 10's with 400 or less HP on 300 TW street tires. Traction will be my worst enemy, as I've got to get car weight down to around 2800 LBs. Transmission used, which is 4L85 based, will be the same as current car because of it 1st, 2nd, 3rd, and 4th gear ratios with 3.55 rear gear. Gearing is what allows those numbers, with the HP engine makes at Rear Wheels. Engine in current car could make more HP, but car is more about looks than performance, so I'll never correct the mistakes that have hurts engines performance, thus car performance.

Firebirdmuscle

iTrader: (16)

It should be quicker OP but what I see that stood out to me first was your running a 3.55 gear and a 28" tire which knocks your overall ratio down even more.

1quikzz

So more gear... or less tire?

poorhousenext

Tire size change from 28.3" to 26.5" will produce also same MPH at 6,000 RPM as 3.77 an 28.3" tire.

2 tires, 2 rims, jack and lug wrench, for track.

If you'll use that speed calculator link I posted earlier, you can play with tire dia & gear ratio to see effects of change in each gear.

Check Tire Mfgs, to see whats dia's or available .

By the way my 4th gear is not 1.00, it's 3.55 x 1.19 = 4.19 effective ratio. I use gearing to make up for lack of HP to help get weight moving.

Firebirdmuscle

iTrader: (16)

Simple to ask but broad to answer. It really depends how you want the car to be. Do you want to street drive more? Or more track? If you want to keep the gears you have now I would definitely bump back down in tire size. But if you going to be more track oriented the 28's will have better traction so to speak becuase they have more sidewall. 28's look better as well but looks aren't everything. How it performs is. If you want to keep the 28's IMO you definitely should re gear for them.

thunderstruck507

iTrader: (18)

If it's spinning "bad" then that's the first thing you need to fix. Spinning destroys ET and if you throttle it to get it to hook then it hurts your MPH too.

FWIW I've been as fast as 11.33 1/4 and 7.2 1/8 with your MPHs on a 1.6 60ft.