Question on modifications

LightEMup

Registered User
Ok, i have a rebuilt engine with 2600 miles on it. New model supercharger no air silencer and a 3 angle valve cut. On a cold night i love how my car runs, hit the gas and it absolutly snaps your head back real hard, but then on a warm day it feels real doggy...what i'm wondering is what it would take to get my car to run like it does on a cold night on a 70 degree day. besides the mods i listed i'm bone stock including exhaust, and i'll be getting portend manifolds and the works fairly soon. Also as a side note, what should i expect after getting ported manifolds and a good flowing exhaust system?
 
You might also want to test your engine sensors (air charge temp., engine coolant temp., and BAP (or MAP, I forget the acronym). The difference in outside air temperatures will make a power difference, but what you describe sounds a little too extreme for normal variation. Maybe one or more of these sensors is wearing out and making the engine unable to adjust to the difference in temperature.
 
I'm going to strongly suggest a double IC, and IC fan. An example in point is this:

dyno tune this last weekend. Two cars, my '92 and a buddy's '94.

Both have very similar mods (I do have the late model supercharger) except roller rockers and double IC with fan.

My intake temps during the 3rd run on the dyno started at roughly 85* and by the end of the run they were at about 95*.

I don't know where my buddy's temp started, but I know that it was up to 150* at the end of the run. He was fighting detonation all day long, and had to get on the dyno 2x to get his car tuned.

Oh, and ambient temp was around 76* for both runs.

And on your exhaust, I wouldn't worry about porting the manifolds. I'm running stock manifolds, and hit 250 rwhp and 340 rwtq. I've got high flowing exhaust after that though. Exhaust is a must and I firmly believe that the IC shouldn't be far behind. It will keep your car from being such a dog on warmer days. And just so you know the friend of mine was only able to get 220~ rwhp and around 310 rwtq.
 
so i should keep the stock manifolds? hmmm ok, ive been debating getting a double IC, i didn't know how well they worked n whatnot....another thing is, i live in maine, so there are some pretty damn cold nights here, a month ago i came out to go to work one saturday mornin, popped the hood to find frost on my intercooler haha, i came down on it in 2nd gear and she broke loose no problem, that's probably why the big dif, HUUGE air temp difference....so after exhaust you guyz think i should go with a double IC and a fan?
 
LightEMup said:
so i should keep the stock manifolds? hmmm ok, ive been debating getting a double IC, i didn't know how well they worked n whatnot....another thing is, i live in maine, so there are some pretty damn cold nights here, a month ago i came out to go to work one saturday mornin, popped the hood to find frost on my intercooler haha, i came down on it in 2nd gear and she broke loose no problem, that's probably why the big dif, HUUGE air temp difference....so after exhaust you guyz think i should go with a double IC and a fan?

I lived in Auburn for 6 years, so I know what you are talking about when you refer to cold mornings....

I'd spend the money on the IC as opposed to the manifolds. They are sufficient to 300 rwhp...above that you are talking serious modifications. If you are like most of us, your mods are not yet serious. Save that money and put it to different (and better resulting) uses on your SC. If you can afford it, go with the MP front mount, if not, then you want to get a quality 2x IC. Don't just buy the cheapest one out there. Pressure testing is key to getting a good one. Make sure that it is pressure tested to ensure that there are no leaks. That's my .02.
 
I couple things some people are either not aware of or have overlooked.

You EEC is the main reason why it behaves poorly once warmed up.

At WOT, the EEC will pull 4 degrees of timing out once the Air Intake Temp gets to 150 degrees. At 135 degrees it'll pull 2 degrees out. I've seen some stock EEC files with this value as high as 8 degrees if Air Charge gets to 180 degrees.

Also at WOT, when coolant temp gets around 220 degrees, it'll pull 2 degrees out and at 230 degrees it'll pull 4 degrees. Conversely, when the cars cold and coolant temp is around 100 degrees or less, it will ADD 2 or 4 degrees to the timing.

So... when cold... it's up to +4 degrees on timing and when it's hot, it could be as much as -8 degrees on timing. Stock tunes generally only run 25-27 degrees max. So cold would be 30 or so, hot would be 13-15. That 12 degree swing is HUGE in how it performs.

Considering the stock tune turns the low speed fan on at 220 degrees and the high speed fan on at 228 degrees, there really isn't anyway to avoid this happening unless you have a chip or tune of some kind. The air charge decrease by an intercooler modification will avoid the 2-4 degree hit from that, but won't do a thing for the coolant temp.

That said, get a better IC, a 180 thermostat and a tune that turns that fan(s) on at 190-195 degrees and it'll be significantly better.

Good luck,
Steve
 
My guess is also at WOT the AF ratio also goes to a fixed amount instead of controlled by the O2 sensors and I am willing to bet it is fat for safety which would benifet a colder engine. has anyone tried repositioning the crank sensor to change base timing?
 
you mean the cam sensor. and a few have tried, but its better to tune the computer to adjust it then to start messing with it. its not a fixed advancement like traditional ignition. you will throw the system off badly by tampering with it, hence the warning "DO NOT ADJUST" on the cam sensor itself.
 
BlackbirdSC said:
I couple things some people are either not aware of or have overlooked.

You EEC is the main reason why it behaves poorly once warmed up.

At WOT, the EEC will pull 4 degrees of timing out once the Air Intake Temp gets to 150 degrees. At 135 degrees it'll pull 2 degrees out. I've seen some stock EEC files with this value as high as 8 degrees if Air Charge gets to 180 degrees.

Also at WOT, when coolant temp gets around 220 degrees, it'll pull 2 degrees out and at 230 degrees it'll pull 4 degrees. Conversely, when the cars cold and coolant temp is around 100 degrees or less, it will ADD 2 or 4 degrees to the timing.

So... when cold... it's up to +4 degrees on timing and when it's hot, it could be as much as -8 degrees on timing. Stock tunes generally only run 25-27 degrees max. So cold would be 30 or so, hot would be 13-15. That 12 degree swing is HUGE in how it performs.

Considering the stock tune turns the low speed fan on at 220 degrees and the high speed fan on at 228 degrees, there really isn't anyway to avoid this happening unless you have a chip or tune of some kind. The air charge decrease by an intercooler modification will avoid the 2-4 degree hit from that, but won't do a thing for the coolant temp.

That said, get a better IC, a 180 thermostat and a tune that turns that fan(s) on at 190-195 degrees and it'll be significantly better.

Good luck,
Steve
What about an EEC tuner, ive heard of em but don't know tons about em. With one of those can you get it to not throw off the timing as much when temps go up? and if you were to do somthing like that does it present a danger to damaging the engine? This is really helpful guyz thanks :)
 
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