After 3 weeks of getting rained out, I finally got 2 runs in at Milan in my new LE2 head/LE3 cam 383. Car is amazingly improved from stock, what a riot! Ran out of time, so really only got one good try.

Temp was about 88F with high humidity - there were thunderstorms in the area and a stiff headwind. This is on Eagle F1 GS-D3s at 35 psi. 3.42 gears. Dyno'd 417 at 6200 on a Mustang with 1/8 turn on stock lifters. Now I'm at 1/4 turn, but my high RPM problem didn't seem to be affected at all by the higher preload.

Run 1 - 90% effort, short shifting a bit:
RT---------0.2301
60'---------1.9971
330'--------5.3192
1/8 ET-----8.0141
1/8 MPH----91.62
1000' ET---10.3110
1000' MPH--106.62
1/4 ET------12.2632
1/4 MPH----115.64

Run 2 - trying hard

Tried to launch at 3k with clutch slip. Wound up flaring the RPMs to about 5k, but little to no tire spin. Unfortunately, the car will NOT rev past 6375 RPM. I thought I was hitting the limiter (set at 6600ish) until I saw my datalogs - it just stops revving suddenly and will not pull through. Edit: I now think this 'problem' was misunderstanding, corrections below.As you can see from the data pic below, I kinda freaked out when this happend, pushed in the clutch, tried again, then gave up and coasted through the traps at 108 mph with a 12.0. Thought the time would suck, and was impressed as heck when I got my slip, considering the coasting part...

RT---------0.5230
60'---------1.8272
330'--------5.1000
1/8 ET-----7.7691
1/8 MPH----92.57
1000' ET---10.0450
1000' MPH--107.59
1/4 ET------12.0399
1/4 MPH----108.18

Here's MPH and RPM graph: I touched the dead zone in 2nd, briefly. Notice how it shows the revs stop climbing BEFORE the mph goes flat in 3rd. Wierd. Injectors stay active but don't go full on, so I don't think fuel pressure is the problem. Gage shows ok on the street. I'm thinking ignition?

Dyno runs showed a ~50 hp power drop at this same RPM range after a few pulls, so it's consistant now but did not exist when we started tuning. Minimal knock at WOT in 1st gear and after 1-2 shift, then none.



So, I'm very confident I can hit 11's even with the problem I have now, by just staying in it in 3rd. But I don't think I'll do that, for fear of hurting something. For now, simply shifting at 6300 will be a big help, but I obviously have to fix this.

What kind of potential do you guys see here? Tell me what you think, please.

 

Most of the LT1 logging software won't show rpms above 6375 (or somewhere around there). It just locks at that rpm, which is why you have flat spots on the top of your 2nd and 3rd gear rpm peaks. It just looks like you held 3rd out longer than you did the other gears.

And, what's the 'dead zone'?

 

Realistically I wouldn't be happy with anything less than 120+ mph traps out of a 6spd 383 heads/cam car.

You won't get that right off the bat and it will take some work and tweaking, but that should be your end goal for the car.

 

What did you use to log your runs? I'm thinking about getting a cheap laptop and some software to do this so I can tweak with my car a little.

 

What he logs his car with (OBDI) will not work for you (OBDII).

 

What was the break down of the firt run? Hard to compare them without all the info.

But 7.76 does usually equal very high 11s or very low 12s, so you likely weren't coasting as much as you think.

 

I'm not familiar with all the LE set ups as far as where they make power, but I'm thinking that 3.42s are not going to bring you near the rpm necessary to get you into your power band...I would think 4.10s at a minimum if not 4.30s, but I don't know where your power peak is...

I'm with Javier that I would think that with the right gear you'd hit 120, or should hit 120 with an M6...

I'm sure you'll work it out...I trap just shy of 120 with 375 rwhp on a Mustang dyno, so 400+ rwhp should put you at 120 depending on weight, weather, driver, etc, etc...good luck...

--Alan

 

Oh but it will, hence the OBDI conversion I have!

 

Well if you put lower gears and a rearend that will hold up to 5k rpm clutch dumps you will be able to run lower 11's but it will take some time to get all working together. 115-116 mph is good for 11's so you need to work on the first half of the track to get the best ET's. Later

 

With some good 50* air, a sixty foot in the low 1.60 or high 1.50 range It should run mid 11's. Just keep picking away at it, do one change at a time and log the change and the result along with track conditions for the change. Good luck.


David

 

Hey, thanks for all the tips and encouragement, guys.

Benji, that's great info on the logging software. Maybe I WAS hitting the limiter, then.


Well, at least enough to hit 115 but trap 108.

As for the first run, I'll fill in the rest of the details.

 

dont think Ive seen you in the local MI/great lakes forum on here? there is a milan track rental tomorrow morning (if I remember right) and another one on sept 15. Im plannin on goin to the 15th rental, and we could line them up! would be fun. you should take me by a .1 or .2 Id guess, but thats IF you can hook all that power. much harder for you M6 guys to launch that hard. take a look at my sig and you'll see were goin to be a good race. plus Id like to see your data logging setup if you wouldnt mind showing me how it works. one day I'll get into that stuff.

chris

 

CORRECTION: My datalogged MPH is obviously wrong above. I had checked the mph vs gps at highway speeds ahd they matched, but I just calculated the gear/rpm/mph and 108 in 3rd is just right with 24.5" tires. So, there is no way I did 115 in 3rd gear like I thought, at even 6600 RPM. Tireburnin was right, I didn't coast as much as I thought. Now I'm thinking there is nothing wrong with my car but the driver, who apparently can't read a tach very well

 

Stock tires are 25.6-7" not 24.5".

 

Speed Demon: Thanks for the info. I simply measured the actual loaded diameter. My 245/50/16s measure 12.25 from the ground to axle center with 35 psi, so I doubled that and used as diameter. Is that the wrong way to figure it? Maybe centrifugal force at speed changes the diameter too much for a direct measurement to be accurate?

IrocSS: Nice to know you. I don't post in the MI forum much, I'll try to check it more often, though. Milan today can't happen, as I have a pile of stuff to do (fix truck, prep dirtbike, hopefully Nugent at DTE) but the 15th might work out if there is a rental day at Milan. If you want to see how the Datalogging and Tuning stuff works I'd be happy to demonstrate. Check your PM's.