LT1 cam, Vortec heads milled .020, Performer RPM intake manifold, 2400 stall.

Run 1: 16.116 @ 89.43, 2.514 60'
Run 2: 15.702 @ 91.81, 2.414 60'
Run 3: 15.500 @ 92.81, 2.412 60'

If you dont want to hear me bitch, dont read past this line.

The goal for tonight was a 14.80 @ 96.00, which obviously was much too low. Im running stock 2.73 gears, no posi, and stock tuning. I had WinALDL hooked up and from the looks of it my fuel pressure was dead on, the highest reading I had at WOT was .906 - maybe a tad rich.

These times were also at Dragway 42, which isnt even a track compared to Norwalk. But Norwalk was closed today for the Chrylser Classic, and this will be the only weekend Im home from school while the tracks are open.

Yea its quite ovbious where the problem is. 93 mph should be good for a 14 if I get a dead hook, and honestly I think there's at least a 94 mph in it as it sits. I have the posi/3.42 rear in the garage, but I might just get a posi unit with 3.73s and have that installed. I didnt change anything at all inbetween the runs, so they just got progressivly better.

Its really agrivating because yea I had high expectations but really I think i should have met them, yet its good because it gives me some aucutal numbers to play with. Oh well my tbi brothers, we shall overcome... it'll just take some extra time on my end lol.

Oh yea, it was so bad that on that 3rd run I had 20 psi of air in the tires and launched at 1200 rpm and still spun that bad. Rough night.

 

That's a fairly impressive mph with a 2.73 diff. It's said for every tenth you shave off the 60 ft time, you can shave 2 tenths off your et.

I imagine that you are making lots more power but spinning off the line too.

At 20 psi in the rears you proably ended up with the v effect on your tires, provided you have good tires, they have stiff sidewalls and what ends up happening the tire curls up and you ride the edges of the tire ala underinflation and get no grip.

The lowest I went was 24 psi on my tires, but they're bfg gforce kdws tires that are made pretty strong.

What size tires are you using and what type?
What rpm do you manually shift at?

Posi, lca's, sfc's and springs would do wonders for traction... or drag slicks. With that kind of power you will easilly be in the high 14's... you just need to get it to the ground better.

I never considered my 2.73's good for drag racing, I actually ended up busting the gears themselves after a good 30 runs on them.

You may want to consider 3.23's with posi, or a 3.27 posi unit to go well with your car. I imagine with the LT1 cam you are making peak torque around 3000 rpm and peak hp around the 5k mark, a higher set of gears would allow you to rev up to those numbers more effectively, less time wasted gaining rpm due to insanely high load number forced by the low ratio 2.73s...

5k rpm is good for 123 mph traps with 3.23s... I know my engine likes my 3.23's... stock peak at 4 k rpm, it hits it about a good 200 ft before the 1/4 miles's end easilly, meaning headers and intake mods that would gain me hp into the 4500 - 5000 rpm range I could easilly find myself doing 1/4 mile runs with high 90's maybe breaking 100 mph if I wasn't surging at the end like I am now.

I shift at 5300 rpm with a stock engine, I imagine since you have more power than me you would be shifting at 6000-6500 rpm...

 

Looks like you are off to a good start.

One thought, forget the O2 readings. Tune your FP for mph. The goal is to run the fastest mph no matter what the O2 says.


PS - What mph did the car run stock?

 

The first run I was at 25.5 psi, and I was freakin pissed when I came back to a 2.514 60', maybe I over reacted lol.

Best I could get stock was 16.60 @ 80.40, then with a cat, cat back, open element, and free mods I went 15.8 @ 84.83. So I picked up 8 mph (at least). Next time I go out Im definatlly going to have posi, lca relocators, and drag radials. Its rough knowing the car has more in it but not being able to prove it.

 

Hey Chuck! after looking in your web site you have a pretty nice setup going on. But I noticed that you have the carb Performer RPM Intake with an TBI adapter, correct? What did you do to the sensors that connected to the original TBI manifold? Also, would that manifold setup be street legal?

Thanks

 

I think if I had to do it again, at least with the stock tbi, I would have just went with the performer manifold (idle - 5500) as opposed to the RPM (1500-6500). Ill never be making hp at 6500, last night I was shifting at 5750 1-2, then 5500 2-D. I would have liked to go a little higher in the rpm, but I was losing traction wise after the 1-2 so I didnt want to go higher. I have a bastard 3.42/posi rear end in the garage, but with school here I dont have time to install it.

Off the top of my head I can only thing of one sensor that had to be plugged into the manifold, the low temp sensor and I had to run some brass fittings out of the front of the manifold. Ill take a picture of it for you today. Its not 50 state legal, no egr. The only Vortec tbi manifold that is is the Chevy one and thats like $299.

 

i would say your fuel is way too high. at WOT you want to see around 650-700, 750 at most if you wanna be extra safe. 900 is waaayyyy rich. you just need it to be a little bit rich to make max power and keep it safe.
did you catch any knock counts on any of the passes? if not, push up teh base timing a little. if you are runnign stock chip still you will prolly only see the knock at idle and low rpm, cause once the cam starts spinning it will eb way ahead of the timing curve anyway.

good work, let us have an update when you get back to teh track. if you are seeing tha tmuch fuel i am sure there are at least 2-3 more mph just in teh fuel pressure, much less any timing adjustmenst you can make. the gears will help a ton with that cam, you must be comin through the traps below 5000rpm(prolly closer to 4500), ideally you should come through the traps a little past peak hp, with teh LT1 cam that shoudl be in teh 5200-5400 range i woudl think.

keep up teh good work.

later
tim

 

Ive always been curious on the fuel pressure. Pablos afpr article says .850-.900 but everyone seems to have their own opinion? Ill back it off a little and see what happens. I pushed the timing till it started to ping then backed it off a little... very scientific way of doing things lol.

 

800+ is good if you are boosted or spraying, but entirely unneccessary if you are n/a. i usually tune into the 700-725.
the timing should be in teh right neighborhood at idle and off the line then.

later
tim

 

You will not get maximum performance from your engine by adjusting FP so the O2 reads a particular number at WOT.

The only way to get maximum performance is to use a method that measures performance. IE mph at the strip, dyno, gtech, vericom etc....

Even if you have a WideBand O2, tuning to a particular AFR will not result in maximum performance. This is because ALL engines make best WOT power at slightly different AFR's. The only way to find out what AFR the engine wants is to measure performance.

Timing is the same way.

 

taht si very very true brent, what we are more looking for is a ballpark to work in though. that gives people an idea of where they want to start and greatly speeds up teh tunign process once they make it to the track.

later
tim

 

The problem with using the O2 at all, is that it is affected by EGT and back pressure at WOT. It is simply not accurate enough to even get things in the ballpark.

Your car may run its fastest at 600mv while the next guy runs fastest at 950mv.

 

i think you are missing my point brent. i don't have a trank in my backyard or a dyno in my garage, i doubt any else here does. i can honestly say taht the vast majority of n/a cars i have seen tuned are at their best under or around 750.
while there are otehr factors taht cause inaccurate O2 readings, they are the best basis the average guy has aroudn everyday to work on tuning their car.


later
tim

 

Heres my log of the 3rd run, I just took the sensor data...

And Tim is right, I just want to have something that people can start off then go from there. So people can also learn from my mistakes LOL I make enough of those.

 

The point is, using the O2 sensor readings for WOT is no better than reading tarot cards.

Its simply not accurate enough for even "getting in the ball park". There is plenty of documentation on this fact. You are better off reading plugs if you don't have the ability to measure performance. Reading the O2 will only waste your time.

 

I'd have to disagree with o2 sensor tuning, I did it today on a dyno and found that at 0.75 I was running 150 hp

I bumped up the pressure, got it into the 0.86 range and peaked at 155.9 HP, o2 sensor tuning does help quite a bit.

My torque and hp curves were A LOT smoother with the bumped pressure as well, if I ran lean I had small spikes, not like a carb does, but it turned out to be a very smooth curve vs my previous dyno runs at a low fuel pressure 0.6-0.7 V...

If you really want to be accurate, take it to the dyno yourself and tune it there.

My car seems to be happy with 2 degrees advance and pressure around 13-14 psi, so coming up next saturday is race day and I'll see how it does.

 

change the rear!!!!






------------------------------------------------------------------------------
1991 Chevrolet Camaro RS
LO3 TBI 305
-GM 305 crate motor (stock internals)
-MSD 6A
-Accel Cap&Rotor Button
-Accel Super Coil
-Gutted Converter
-30 series 3 inch Flowmaster Catback Exhaust
-Hypertech Street Runner Chip
-Edlebrock Air Cleaner
-K&N Air Filter
-Moroso Breather Filter
-Summit Racing Valve Covers
-3.42 open rear from a 1985 2.8 V6 Camaro (RIP)
-Removed all Emissions BS
-160 Degree Thermostat

Best ET to date 15.53@87mph 60' foot=2.09

 

thats gotta be a problem. carb it

 

lol brody.. Ima run this tbi thing for a while. Im a nerd so naturally the computer intrigues me

 

lol alright, what about custom chips though

 

Hopefully Ill have the money to buy the programmer and tuner cat or something around xmas when I start working a little again. Im playing around with this free little editor for the 8746 just trying to figure some stuff out, but I cant burn any chips so its kinda for nothing. Money is just the brick wall...

 

i feel ya

 

Brent is absolutely right

I wrote that article like 5 years ago when no one really knew any better including myself. Id like to change it but hey i have a pretty busy schedule and im no longer in regular contact with the webmaster

While you wont burn your engine down because of a lean condition with your o2 values up that high (well.. generally... o2 values are not universal for all cars)

its not neccessarily where your best power is. Its not even consistent. Its affected by numerous variables, temperature being a big one. Exhaust temp changes dramatically through a drag run and hence your o2 voltage is affected accordingly.

best bet is to get yourself into a wide band o2 sensor setup and an EGT. Youll see what i mean with the EGT.

My car can run anywhere from like **** to stellar with the o2 values looking the same on different tunes.