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bct10985 05-13-2013 05:37 PM

timing and iat
 
Those with centrifugals what kind of iats are you seeing and what is your total timing at wot?

BullF-16 05-13-2013 08:32 PM

My timing was about 17-19 deg at WOT with IATs at about 115-120.

Pat G, my tuner set it up to pull timing at IATs above about 55 deg C or 135F

Fully built/forged motor though!!!!!!!!!!!!!!

AFRs were very conservative at 10.8-11.0

dan0617 05-13-2013 08:41 PM

Timing depends on IAT in my tune. On a 65 degree day, I see IAT at the top of 2nd gear at 114 degrees and timing at 14.5 degrees. By the top of 3rd I see IAT at 159 degrees and timing at 11.5 degrees.

I am surprised to see timing pull that much with that temp but I guess that is what is safe. I'm also surprised to see IAT's climb that much, but is still better than the top mounts I've seen. This is with a Vortech Si trim ECS kit, 12 lbs of boost on a stock cammed L99.

What is everyone else seeing for IAT's after a 1/8th or 1/4 mile pull in 60 or 70 degree weather??

bct10985 05-13-2013 09:44 PM

My iats were getting up to 160 on the dyno and my tuner said it would only accept 8 degrees of timing before knock sensors would pull timing. He acted kinda shocked and asked what octane and where i got the gas from. Royal farms 93.

dan0617 05-13-2013 09:48 PM

I am at 11.2 AFR running 93 octane 10 percent ethanol. Gauge set for 14.2 stoich. I am down to 11.5 or 12 degrees timing at 160 IAT. 6200 rpms 12 psi boost. No knock retard.
Stock l99 stock cam.

8 degrees seems a little low. Make sure your AFR is no leaner than 11.7 with normal gas calibration and fuel that has ethanol blended.

realcanuk 05-13-2013 10:31 PM

Quote:

Originally Posted by bct10985 (Post 6540242)
My iats were getting up to 160 on the dyno and my tuner said it would only accept 8 degrees of timing before knock sensors would pull timing. He acted kinda shocked and asked what octane and where i got the gas from. Royal farms 93.


I dont think IAT's should get that high with a centri. Even with my eforce I never see 160.

I am running 94 octane, 10% ethanol, , 12 lbs of boost, 18 degrees of timing, and afr around 11.8 . This is on a forged motor and meth, which can obviously take more timing than a stock engine.
By 158 I am pulling a ton of timing, just in case but I never expect to see those temps.

bct10985 05-14-2013 07:45 AM

Matt from fsp thinks it could be that their dyno didnt have good enough airflow and that you would never see iats that high on the street. I dont know why im looking for more power the thing just blows the tires off as it is lol

Padre 05-14-2013 08:33 AM

With ported heads, 9.5CR, stage II intercooler, and 104 unleaded, I see 160* (at 6800 rpm and 130mph+ at the top of fourth) and 18* timing with no knock-reduction. :)

Padre

dan0617 05-14-2013 08:58 AM

I see 160 IAT on the street at the top of 3rd after a WOT pull starting from 1/2 way through 1st gear. Not the dyno.

dan0617 05-14-2013 09:02 AM

With an air to air IC centri, or with a normal intercooler on a top mount, I'm betting there isn't a setup out there that stays below 160 IAT on a 70 or so ambient day.

Everyone I see below 160 is fancy intercooler, AC setup, meth, etc.

dan0617 05-14-2013 09:06 AM

Quote:

Originally Posted by realcanuk (Post 6540477)
I dont think IAT's should get that high with a centri. Even with my eforce I never see 160.

I am running 94 octane, 10% ethanol, , 12 lbs of boost, 18 degrees of timing, and afr around 11.8 . This is on a forged motor and meth, which can obviously take more timing than a stock engine.
By 158 I am pulling a ton of timing, just in case but I never expect to see those temps.

Cam and compression have ALOT to do with timing. Meth has ALOT to do with IAT. Turn the meth off and let us know what your IAT and timing is at the end of a 1/4 mile run just before you lift off the go pedal. Ill bet you see well over 160.

Alvin@PCMofNC 05-14-2013 09:38 AM

Quote:

Originally Posted by bct10985 (Post 6540242)
My iats were getting up to 160 on the dyno and my tuner said it would only accept 8 degrees of timing before knock sensors would pull timing. He acted kinda shocked and asked what octane and where i got the gas from. Royal farms 93.


I would make some changes ASAP. A good cam will allow you to run more timing at the same boost than the stock cam..Especially if you have a L99. Please let us know if we can help with the cam.

Other than that I would go up on the pulley size (less boost) I feel really uncomfortable if I cannot get at least 12-14 degrees of timing in a setup and the reason is this...

Combustion releases energy in a combination of two ways. 1. Expansion work (good) 2. Heat (not so good) The later the timing the more the combustion cycle misses out on expansion work because the majority of the expansion happens relatively soon in the cycle at around 28-35 degrees after top dead center. So what is happening the energy released misses its chance to be expansion work and so is only option is to become heat. This is putting more heat into the exhaust valve, plugs, headers/manifolds, cats, etc!

What I'm getting at is the later the lead, the more your going to start cooking everything else!

realcanuk 05-14-2013 10:01 AM

Quote:

Originally Posted by dan0617 (Post 6541657)
Cam and compression have ALOT to do with timing. Meth has ALOT to do with IAT. Turn the meth off and let us know what your IAT and timing is at the end of a 1/4 mile run just before you lift off the go pedal. Ill bet you see well over 160.


I had my supercharger without meth for over a year.... saw about 140 at the end of a run. .

bct10985 05-14-2013 10:29 AM

Quote:

Originally Posted by Alvin@PCMofNC (Post 6541755)
I would make some changes ASAP. A good cam will allow you to run more timing at the same boost than the stock cam..Especially if you have a L99. Please let us know if we can help with the cam.

Other than that I would go up on the pulley size (less boost) I feel really uncomfortable if I cannot get at least 12-14 degrees of timing in a setup and the reason is this...

Combustion releases energy in a combination of two ways. 1. Expansion work (good) 2. Heat (not so good) The later the timing the more the combustion cycle misses out on expansion work because the majority of the expansion happens relatively soon in the cycle at around 28-35 degrees after top dead center. So what is happening the energy released misses its chance to be expansion work and so is only option is to become heat. This is putting more heat into the exhaust valve, plugs, headers/manifolds, cats, etc!

What I'm getting at is the later the lead, the more your going to start cooking everything else!

Its an ls3

dan0617 05-14-2013 12:31 PM

Quote:

Originally Posted by realcanuk (Post 6541817)
I had my supercharger without meth for over a year.... saw about 140 at the end of a run. .

If you were running 12 psi on a top mount blower and no fancy intercooler tricks and no meth then you have an amazing blower to top out at 140 IAT at the end of a 1/4 mile pass. Guys running 7 psi are getting hotter than that on those blowers.

realcanuk 05-14-2013 03:08 PM

Quote:

Originally Posted by dan0617 (Post 6542309)
If you were running 12 psi on a top mount blower and no fancy intercooler tricks and no meth then you have an amazing blower to top out at 140 IAT at the end of a 1/4 mile pass. Guys running 7 psi are getting hotter than that on those blowers.


Most of my scans are on my laptop but here is an old one. No meth, a hot day in the middle of summer, but only 10-11 psi because belt was slipping.

147 IAT... guess I have an amazing blower....:biggrin:

I am not saying I run so much cooler... I just thought from all the PD blower bashing I see in forum, that centri's ran nice cool IAT's

http://i1122.photobucket.com/albums/...ps0b95bc45.png

dan0617 05-14-2013 06:44 PM

Quote:

Originally Posted by realcanuk (Post 6542978)
Most of my scans are on my laptop but here is an old one. No meth, a hot day in the middle of summer, but only 10-11 psi because belt was slipping.

147 IAT... guess I have an amazing blower....:biggrin:

I am not saying I run so much cooler... I just thought from all the PD blower bashing I see in forum, that centri's ran nice cool IAT's

http://i1122.photobucket.com/albums/...ps0b95bc45.png

Awesome. Was this with the stock cam? If so I guess I should have bought an Edelbrock instead of a Vortech.

Odd that the IAT stayed dead flat at 147. I've never seen that happen. I always see it increase as the pull continues.


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