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I just got my '71 Firebird dyno tuned last night, it has a LSA out of a 2013 CTS-V with 2.55 upper pulley and LS9 camshaft, and LT headers (1 7/8) and of course a cold air intake.
The weather was HOT!, it was 105F with no less than 80% humidity, the DA was 3400+. The IAT2 temp was through the roof at about 170F. The results were low numbers as expected :
573hp@6200 / 604 ft/lbs@4000sh (not sure). The same engine setup was dynoed last winter in 50F day and it put down 623hp. Does the hot weather and high IAT temps affect the power that much? I mean I expected less numbers but 50hp is a big difference!, will I get back the lost horsepower in a cold day and lower IAT or do I need to re-tune it again in winter?
The timing is probably reduced via the iat table(ability to add or remove timing based on iats... I can easily see 50rwhp drop if it’s pulling 8-10 degrees... especially if iat’s Are 170+.
Here are a few pics right after I went back from the dyno shop. I was playing with a Porsche 911 driver on my way back from the shop and sure enough he was shocked!
The car was an all original 1971 Firebird Formula 350 with stock engine and TH350 trans. Now it has a LSA with a magnum T56 and a FAB9 9 in rear end. I will get it soon out to the drag strip, I hope I can get it into low 10s.
That's a very beautiful car. Don't discount the impact of humidity also. I've seen a car in dry air go to humid air and at the same map readings, temperatures, dynamic airflows, etc, the fuel trims and WB error went negative, indicating it was getting less oxygen and cutting fuel. It was around 3% average difference due to humidity. At 680 HP, that's 20 HP approx.
The dyno should be correcting for the temp and humidity. Both sae and std correction factors will compensate for the air. The iat's being 170 are probably what is causing a power loss. I have tuned dozens of lsa's and ls9's. At 170 iat on 93 octane you need to be pulling 7-8 degrees from the base timing table through the iat table. That's easily 50 whp and then some vs. 100-120 iat.
Do they make a phenolic spacer for the LSA blower? if so, that might drop you air intake charge and get more hp.
Fasterproms sells what they call thermal plates for the LSA blowers, among other things. Might be something you wanna look into, as they just made over 700rwhp with an old LSA blower on a 6.0.
09-26-2018, 04:57 AM
Dyno results in 105*F , 80% humdity and 3400 DA! 
