I just dropped my truck off today to have a FMIC put on my Denali that has a whipple supercharger on it. I am currently running 12psi and don't plan on changing pullies right now. How much of an increase in power should I see?

 

FMICs don't make power. That is like putting in larger injectors they also don't make any power. But what they do is support more power. With the intercooler it allows you to increase the boost or add timing which in turn will make more power. Unfortunately though on the supercharger the FMIC will probably lower your boost by a lb or two(depending on size and efficiency) thus making less power since you don't plan on upping the boost. If you add some timing it might out-weight the power loss though.

Change the pulley to make more boost and then you will see more power.

BTW, the turbo also looses some boost with the addition of an intercooler but if the wastegate is referenced to the intake manifold you will not see a drop because less air goes out the wg instead.

 

I was heat soaking pretty bad and seeing some pretty high IAT at times up to 240-250. My timing was being retarded 8-9* at higher Rpm's near the shift point. I figure I should be making more consistant power and better top end with the intercooler.

 

What he said is pretty close to what happens.I have a whipple with a front mount intercooler.I lost 2lbs. with the addition but,it did not lose any power it gain a little.Went from 9.5lbs. to 7.5lbs.Then I droped the pulley size to bring it back up to 10-11lbs.I can not give you the power difference but,there was a noticeable SOTP difference.I was maxing the maf out at 5500 rpms.Started blowing the heads off too on a cold night when it hit bout 12lbs.

 

This statement is deceptive. I agree that FMICs don't "make power". But in stock form a whipple isn't intercooled. Pumping out 12psi is going to generate quite a bit of heat (240* IATs as posted above). The benefits of adding a FMIC should result in a really nice gain in power. IATs could drop 150* in this situation.

Also, just increasing boost doesn't necessarily mean more power. Higher IATs, less timing, detonation could easily negate any benefits from higher boost.

Boost is just a measure of pressure. Hot air expands, increasing pressure, but that increased pressure doesn't add any more air mass, just volume. If you aren't adding additional oxygen molecules to the party, then combustion potential hasn't increased either. 12psi of 240 degree air could easily have less mass than 10psi of 80 degree air. Personally, I'd rather have 10psi @ 80* than 12psi @ 240. Been there done that.

 

Exactly this is the reason that I decided to go for the intercooler on. I am expecting it to significanly lower the IAT which as a result should make more power at the same RPM especially with 9*KR and 240* IAT before.

 

You will not know for sure until you take it to the dyno.

This is all speculation but if lets say you get 15hp per lb of boost and you lose 2 lbs with your FMIS then you lose 30hp. Now you said you get 9* retard so lets say that for each 1* of ret/adv you increase/decrease hp by 4hp then you would gain 36hp. That would give you a net gain of 6hp.

You might gain more because besides putting the 9* of retard you might also be able to put more timing in but again this is all speculation. You might make more per lb of boost say 20 or you may gain more per 1* of timing. Maybe your FMIC is so efficient that you only lose 1# or maybe you will lose 3# who knows.

If you change the pulley to get back the boost you loose with the FMIC then you will really gain and still lower you IAT's. That is the best of both worlds.

 

A dyno is going to be hard to find but I remember when the tuning was being done EFI Live the program that was being used said it was estimating my hp lower when I upped the boost most likely due to the higher IAT and KR. I think that the intercooler will help make my setup more efficent. I went with a percision intercooler core that was sized properly and not much more than I will need. These guys are making making the intercooler kit for me and tuning it.http://www.hutterperformance.com/default.aspx There shop has some pretty serious cars in it so I am sure they can handle this job.

 

I still disagree.

It doesn't matter how much 'boost', but rather how much air mass is getting into the engine. Cooling the air temps down 150* will reduce pressure (boost), but there are the same amount of air molecules in there, they are just more densely packed. Power wouldn't change because boost was lower (it should increase because of the IAT / timing benefits). As long as the supercharger still pushes in the same amount of air, don't worry about a decrease in boost.

 

I disagree also.

Here is some info I have for that.

"Supercharger output is fixed and doesn't increase merely because downstream air charge temperature is lowered. It's the same air by mass. The mass, the weight, the oxygen content of that blast of air discharge by the supercharger cannot be increased. You don't believe it? Try this. Capture the discharged air in a bottle, seal it and weight it at 300*, 200* and -50*. The weight(mass) will not change, the engine can't ingest more air so it will not make more power. Yes, the cooler denser air, at -50* will allow more boost and/or more timing but that air by itself will not make more power.
Now if the air(ambient) temperature entering the supercharger is reduced like driving in Alaska instead of Arizona then the cooler denser air will make more power. About 1% increase for every 10* temperature drop."

That is why I say if he changes the pulley to get back the lost 1-3 lbs do to the FMIC then he would definitely see some good gains. Not doing so might get him a little but you are robbing Peter to give to Paul so to speak.