Hole-Shot

Here is a little background on the subject to bring you up to date.
Last fall after putting in a new Vigilante 2600 torque converter, I ran several 11.8xx @ 116-117 mph. My 60' times were in the 1.5xx range. These runs were with a 383-bottom end, ported stock GM intake, AS&M Runners, stock ported plenum, and an AS&M 52 mm throttle body. At that point, I was very happy with the performance of this long tube motor. 11.8xx. @ 116-117.

After a lot of deliberation, I decided to swap out the stock style TPI components and install a SuperRam. All indications are that the stock style TPI is too restrictive and the SuperRam is a superior intake, (especially for a 383 with a 219 cam.) I figured that by installing the SuperRam I could run mid 11's and add a couple of MPH to my trap speed.

All of the SuperRam components I installed were carefully ported & gasket matched to each other. All internal rough casting was removed and smoothed out of the Acell intake manifold and runners. The plenum is port matched to the runners. I also came across a good deal on a 58mm Acell throttle body, so I added that into the equation. While I had everything pulled apart, I had my fuel injectors re-built/flow-matched.

After I completed the installation, needless to say I was very eager to test the results, so off to the track I go. The weather was "Ok", 80 degrees and sunny, dew point of 55, humidity 47%, pressure 30 inches and steady. I only got 2 runs in before eliminations started due to all the events taking place at the track (lots of people busting parts and dumping oil all over the track.)

My first pass I spun off the line and ran a 60' @ 1.845 and ended up with a 12.258 ET @ 114.44 mph.
My 2nd pass I hooked up solid and ran as follows:

60'=1.625
330 = 4.891
1/8 = 7.633
MPH = 89.96
1000 = 9.983
¼ = 11.951
MPH = 114.82

For comparison, here is a run from last fall with the TPI long tube intake.

60'=1.56
330 = 4.818
1/8 = 7.597
MPH = 90.92
1000 = data not shown
¼ = 11.836
MPH = 117.26

Ouch! My car runs slower with a SuperRam !?! (.12 slower et. & 2.4 mph slower) How can this be? I really thought that I would see some sort of improvement in my performance. It is quite disappointing considering the amount of effort and $$ that I put into it all.The part that bugs me the most is the drop in MPH.

A couple of post-install observations:

· Motor seems to run a bit more "lumpy" on idle. Almost as if it has a more aggressive cam, (no cam change was made.)

· Car feels strong. I didn't notice any real change in the SOTP performance characteristics...possibly a bit more pull in the higher RPM's.

· No visible leaks of any fluids from the intake or any other area that was changed.

· Possibly a very slight hesitation off of idle.

· An occasional "pop" after letting off the gas, for instance if I rev it in neutral. This never happened with the long-tube runner intake.

· No audible hissing or vacuum leak sounds.

· Running custom chip made by a fellow Corvette Forum Member. (could need to be tweaked)

· Shifted at approximately 5800-6000 RPM with converter locking up mid 3rd gear.

· Ran with the timing @ 4 btdc to avoid spark knock (played it on the safe side w/11:1 compression) Advancing the timing never seems to effect my performance one way or the other.

On the upside, I did get some compliments on the appearance of the motor.

I am baffled at this time. I am in need of some suggestions here. What could some potential issues be?
Any input on this will be appreciated. Thanks.

GiDvEtTe84

What are you doing for more fuel? What kind of custom tuning do you have? Thanks. :seeya


[Modified by GiDvEtTe84, 12:17 PM 7/1/2003]

Corvette0096

I bet you have to have your chip adjusted..

_freakmonkeydogboy_

:withstupid:

SBNova

Im concerned about the POP you said you have. Usually this indicates a lean situation. Other than that, what gear ratio do you have in the rear? I see alot of C4 guys running 2-3.07's and wondering where there ET went. ET is more about gearing,suspension and traction. MPH is the true indicator of horsepower. Your new ET's show a drop in MPH- that may be due to the mixture, the drop in ET may also be the mixture but might have something to do with decreased torque as well.

Hole-Shot

It doens't pop all the time, it did it a few times which is a few times more than it ever did previously

I am running a 3:45 rear gear. My RPM's stay up over 4000 rpm after a shift, so that should rule out any loss in torque (since the long-tubes pull a tad harder in the 3000 range.)

Still scratching my head :(

J Z06

Did you have the car re-tuned? Also it could be the warmer more humid air that might have slowed the car down. Heat and humidity are killers. It should run much better with the SR on top.

MrNuke

:withstupid: The superram should have not lost much torque on the low end either, but should pull NOTICEABLY better after 4K... Mine sure does...

0ski_dwn_it

There a zillion things that could be effecting your tune. BeachBum Runs the same combo and his normal ETs are around 12.6s, with Good 1.5 hooks. With that kind of short time you would be at 12.7s.

Are you running drag radials or slicks?

skinnies up front?

Just for the record there I am the one that did the tuning of his car. And at the time of the tuning it was done for long tube runner and a 52 mm TB. So there is a new SR and 58 mm TB thrown in that wasn't accounted for.

Surely we can tweak it a little to get some more power out of it, but I want to see where we stand. Weather etc can play a HUGE role in making one mod look worse than it really is. Given equal DAs. The car might be .2 sec quicker as is. THis is what we need to find out.

Is there any weather comparisons....ie off the time slips etc.

Also you should be shifting at about 5600 RPM max with that setup.

I would also suspect that you might be getting some knock, since the tune was setup for less air flow, and with the SR its gonna breath much better, hence a slightly leaner mixture that might promote some knock counts, and that will definately kill power.

Your running a pretty stout compression ratio and to effectively get more power out of it and keep from tripping the knock sensor you might have to run some higher octane. I would like to see what your ET are with a gallon of Toluene mixed in with about 7 gallons of fuel. ( that is what I run in my car, but a much higher concentration). To see if your getting any retard or not before we redo your chip.

I would bet your MPH climb about 3 MPH with the toluene mixture....can we try that?

Let get some answers to these questions and see what we can turn up! :cheers:


[Modified by ski_dwn_it, 3:14 PM 7/1/2003]


[Modified by ski_dwn_it, 3:16 PM 7/1/2003]

Beach Bum

Holeshot, I think you might have other things going on here.... as you know on your original timeslip with the long tubes, I've never liked that slip.... with a 1.56 60ft and 117 mph trap speed, that should have been a solid 11.5 timeslip, but I think you were having tranny problems maybe as I recall ??

But this new timeslip has the same problem....a 1.62 60 ft with a 114.8 mph should be an 11.7 timeslip.... doesn't make sense. Have you ever run at a different dragstrip ? Also looking at your slips from a comparison point of view.... on your faster timeslip, you start off with a 1.56 vs 1.62 60 ft which is a 6 hundreths advantge, then at the 330 ft mark, its a 8 hundredths advantage, but then at the 1/8th its only a 4 hundreths advantage even though the mph was higher..... something strange.

In any regards, not sure why you're running slower.... if you can name the track and 2 days that you raced in to get those 2 timeslips, I can check the weather history to find out what kind of a variance we have. Also name the approxmiate times of the day you ran them. What is the closest city to the track.

In any regards, I am sure you will get it ironed out with some tuning... you should have several more mph with the Superram and maintain roughly the same 60 ft.... however a bit more stall would be beneficial considering you have moved up your torque peak 500 rpm or so.

gotta go

later
Beach

0ski_dwn_it

I just went back and looked at some WOT runs on my car....My RPMs drop well back below 4000 in third gear. But my gears are 3.07s. But I would think that you would drop below 4000 RPM there also....is it possible that something might be slipping a tad?

Check your tranny fluid level. As Beach said something sounds a little fishy with a few things here.

:cheers:

Hole-Shot

I will try to answer a couple questions here:

I run at the Legendary Great Lakes Dragaway in Union Grove Wisconsin. I have never run at any other track.
I run with dot approved slicks, with the stock fatties up front. My fluid levels are exactly on. I always check them
When I made the 11.8 @ 117 runs (October 27th 2002) going off memory the temperature was in the mid 50’s.
The temperature for my latest runs (June 29 2003) was around 80 degrees. It was a nice day. Humidity was low.

All issues aside from the tuning aspect, what could the probability be (given the strange numbers on the time slip) that I have problem related to the transmission, namely the valve body? Could the valve body been messed up when the shift kit was installed? Could the fluid not be passing through the chambers as efficiently as it could/should at certain points? I question it because if I rev the motor in neutral when I am coasting (lets just say @ 35 mph) the car will “lurch” forward. It will also do this “lurch” at a stand still. Maybe it is just the torque of the motor. My shifts feel firm, it chirps the wheels when it shifts, and from a standstill on dry pavement it will fry the wheels all the way through 1st and 2nd gear.

Thanks for the feedback Gentlemen !

GlennS87

It seems to me that the weather conditions were significantly different which would account for most of the mph differential. I would imagine a smaller portion of the difference would be related to a chip that is not optimized for the SR/219 combo.


[Modified by GlennS87, 9:35 PM 7/1/2003]

Hole-Shot

When I plan on heading to the track I add a couple gallons of toluene or Xylene. I try to leave for the track with a 1/4 tank, that way when i get to the track I only have a couple gallons left.

When I get to the track I put in 5 gallons of 100 octane unleaded race gas.

I will hook up the Diacom and see if I am getting any knock counts. :cheers:

CORKVETTE1

I THINK THE WEATHER ALONE COULD BE 2-3 TENTHS :cheers:

Vic'89

The way I see it is as follows:

Holeshot should have picked up 2-3 tenths with the superram in the same weather condtions, right ? Now, the weather was worst than last time, so he should still run the same # as the LTR's (117 mph).

I don't think the tune is that off.

Also, what were your shift points with the LTR's ?

Vic

GiDvEtTe84

Whats your FP?

Hole-Shot

That is a very good point about at least staying appoximately the same mph.

My shift points with the long tubes was 5300-5500 with the rpms not dipping below 4000 rpms after the shift.

Vic'89

Are you going to take the car to the track agin for some testing ?

Vic

BBA

Well...if you noticed a difference in idle roughness...with the same cam...there must be a difference in tune. Combine that with a difference of 30º air temperature...all bets are off. Your tune could probably be better.