Which SuperCharger and WHY
06-10-2009, 12:14 PM
#43
5th Gear Member
Join Date: Mar 2007
Location: Florida
Posts: 3,062
Yeah just let me know man, and when I decide to sell I'll be sure to check with you first. As of now, next summer is probably what I'm looking at anyway. I'll have to take a loss on the car in terms of payoff, and I have a bunch of other stuff I want to do financially between now and then (we have a 15 year old turning 16 this year, so might buy a car for her, etc etc). I would estimate it'll have less than 5000 miles on it in a year...
06-10-2009, 02:21 PM
#46
2nd Gear Member
Join Date: Jul 2008
Location: Billings, MT
Posts: 462
I would do the 2.8L Mammoth for the GT500.. 725 flywheel hp on pump gas!
06-10-2009, 02:25 PM
#47
2nd Gear Member
Join Date: Jul 2008
Location: Billings, MT
Posts: 462
06-10-2009, 02:40 PM
#48
2nd Gear Member
Join Date: Jul 2008
Location: Billings, MT
Posts: 462
The only time I've really seen "heatsoak" was a couple weeks ago when I went out for a drive on a Saturday afternoon for a few hours and it was around 100 degrees outside. The IATs were running around 140 degrees and the few times I stepped on it, I could definitely tell it was compensating. It was still pretty quick though, and the tune appeared to do exactly what it should have. The car is only a weekend toy for me, so this condition isn't something I encounter often enough to worry about. Even with the intercooler, I think the IATs would have been 115+ or so that particular day.
The other thing to consider is, depending on the tune, as intake air temp increases, the computer will pull timing to prevent detonation. As IAT increases, the chance of detonation increases, and a safe tune will start to pull timing if the IAT is getting into that 140 degree range. So if it pulls 3 or 4 degrees of timing, you lost another 15-20 horsepower. If it pings, your timing will shoot back as far as 25 degrees, killing your power drastically.
The centris don't suffer from heat soak as much as positive displacement superchargers, so a non-intercooled twin screw in a 100 degree day would probably see 150-160 degree IAT's.. With an intercooler you can easily get that down to 115-120, gaining 30+ horsepower easily, not to mention the 20-80 hp you will lose if you get a detonation or just from the tune pulling timing to be safe.
The KB tune is pretty safe, but if your gas isn't 91 or higher, you will ping when it's all hot, particularly at WOT at lower rpms. When my intercooler wasn't working and it was hot out, my butt-dyno told me I was pushing maybe 330 hp to the wheels.. over 100 hp loss easily. But with the IC water not circulating, the IC was heating the air instead of cooling it, and probably pushing the IAT to over 180.. then the pings would pull timing and the engine turned into a dog.
Heat soak can really have a huge effect under the right (or wrong) circumstances.
06-10-2009, 03:11 PM
#49
2nd Gear Member
Join Date: May 2009
Location: utah
Posts: 305
I don't have time to find the actual math, but somewhere on KB's site they have the relationship between IAT, Boost, spark advance, and octane. I believe that 20 degrees intake air temp is equal to 2/3 psi boost or about 2 degrees of timing (could be off on that, not positive).. So the power you lose from 115 to 140 is more than the equivalent of a pound of boost, which equates to over 20 hp at the wheels (in a 4.6 a pound of boost is about 16 rwhp).
The other thing to consider is, depending on the tune, as intake air temp increases, the computer will pull timing to prevent detonation. As IAT increases, the chance of detonation increases, and a safe tune will start to pull timing if the IAT is getting into that 140 degree range. So if it pulls 3 or 4 degrees of timing, you lost another 15-20 horsepower. If it pings, your timing will shoot back as far as 25 degrees, killing your power drastically.
The centris don't suffer from heat soak as much as positive displacement superchargers, so a non-intercooled twin screw in a 100 degree day would probably see 150-160 degree IAT's.. With an intercooler you can easily get that down to 115-120, gaining 30+ horsepower easily, not to mention the 20-80 hp you will lose if you get a detonation or just from the tune pulling timing to be safe.
The KB tune is pretty safe, but if your gas isn't 91 or higher, you will ping when it's all hot, particularly at WOT at lower rpms. When my intercooler wasn't working and it was hot out, my butt-dyno told me I was pushing maybe 330 hp to the wheels.. over 100 hp loss easily. But with the IC water not circulating, the IC was heating the air instead of cooling it, and probably pushing the IAT to over 180.. then the pings would pull timing and the engine turned into a dog.
Heat soak can really have a huge effect under the right (or wrong) circumstances.
The other thing to consider is, depending on the tune, as intake air temp increases, the computer will pull timing to prevent detonation. As IAT increases, the chance of detonation increases, and a safe tune will start to pull timing if the IAT is getting into that 140 degree range. So if it pulls 3 or 4 degrees of timing, you lost another 15-20 horsepower. If it pings, your timing will shoot back as far as 25 degrees, killing your power drastically.
The centris don't suffer from heat soak as much as positive displacement superchargers, so a non-intercooled twin screw in a 100 degree day would probably see 150-160 degree IAT's.. With an intercooler you can easily get that down to 115-120, gaining 30+ horsepower easily, not to mention the 20-80 hp you will lose if you get a detonation or just from the tune pulling timing to be safe.
The KB tune is pretty safe, but if your gas isn't 91 or higher, you will ping when it's all hot, particularly at WOT at lower rpms. When my intercooler wasn't working and it was hot out, my butt-dyno told me I was pushing maybe 330 hp to the wheels.. over 100 hp loss easily. But with the IC water not circulating, the IC was heating the air instead of cooling it, and probably pushing the IAT to over 180.. then the pings would pull timing and the engine turned into a dog.
Heat soak can really have a huge effect under the right (or wrong) circumstances.
