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Old 02-18-2014, 11:46 PM   #1
g8lover
 
Drives: Pontiac G8 GT
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Higher IAT after engine rebuild- procharged

Hi,

I have a Pontiac G8 with a 427 LSX fully built with a 4L80 and a procharger F1d running about 16-18lbs.

I always fought higher IAT running about 180 or so end of dyno run. Ended up going from a 3 core procharger Air-Air intercooler to a 1300 procharger Air-Air... massive improvement and now only up to 120 F or so on dyno and power way up... was at 860rwhp on a mustang dyno.

Was going to the track last fall for my first run after the improvement and my 4L80 died on the way to the track... (apparently my converter was made wrong and sent crap into my trans and messed up the pump... ) So over the winter pulled the trans and the engine for a rebuild.... figured good time for a engine checkout... billy briggs refreshed it with better pistons, jesel shaft mounted rockers, etc....

All back to together and on dyno now.... IAT now up to 180 after each run with pulls enough timing to drop power to around 800rwhp....

Checking out all the obvious stuff, but what could cause this.... procharger looks good, nothing in intercooler looks different and cooler pressure tested and all good... running 16-17 lbs... engine sounds great....

immediately after being under high load it will drop immediately down to 100-105 degrees.... so quick that it is still in the slowdown portion on the dyno....

No idea whats going on.... had old race gas (MS109) in it from back in sept but cant see how that could effect it.... maybe?....

anyother possibilities.....?.... is there anyway the engine could be pushing heat back to the sensor?....

Not doing a meth system as it was fine last year.... looking for something that could have changed that could effect IAT's.....

Thanks for any thoughts!!!
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Old 02-19-2014, 05:27 AM   #2
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Are ambients and all other times same as previous ?

Can you swap the sensor in case it is faulty ?
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Old 02-19-2014, 08:02 AM   #3
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They always get hot on the dyno due to low airflow across the intercooler.
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Old 02-19-2014, 08:08 AM   #4
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Get better/bigger fans then ! lol
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Old 02-20-2014, 09:40 AM   #5
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Quote:
Originally Posted by stevieturbo View Post
Are ambients and all other times same as previous ?

Can you swap the sensor in case it is faulty ?
I would check that first too.

Since Air/Air intercoolers vary so much you need to check the start and ending both temps. If it gains say 40 degree's over the run but starts at 140...yeah it probably would hit 180 by the end of the run. At the same point, if you started at 80 degree's the end of the run 120 wouldn't be out of the question.

Do you have any of the logs recorded to see gains over the run...both the old run and new one?

Same fan blowing on it?
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Old 02-21-2014, 11:17 PM   #6
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Thanks for the ideas...

Already swapped sensor and reads the same.
Same ambient temps before runs last yr and this yr....
Same IAT temps at start of run last yr and this yr...
ending temps at full power 180 this yr.... 120 last yr....
same fans blowing in same spot on intercooler......

only thing different is the engine was pulled and so was trans... both were redone..
checked intercooler, procharger, intake for blockages or restrictions... nothing found
Procharger checked out and looks all good...
Coolant temps look normal--- same as last yr...

Anyone have similar setup (16-18psi boost...)(procharger)....?... what are your temps just at full boost during dyno run?... as soon as run is over within seconds it drops way down to 105 or so..
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Old 02-21-2014, 11:19 PM   #7
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I would check that first too.

Do you have any of the logs recorded to see gains over the run...both the old run and new one?

Same fan blowing on it?
going to try to get some logs.... ...

same exact fans directed in same spot.... same distance away...
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Old 02-22-2014, 02:17 AM   #8
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Well it sounds like the sensor is working correctly.
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Old 02-22-2014, 11:39 AM   #9
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Is it possible if the engine isnt setup right with regard to pushrod length, short travel lifters, valve lash settings?..... maybe valves arent being opened enough and wont let it flow as well and then heat up.... then build up heat back up into intake pipe?..... I am not an engine guy so I am just trying to grasp at anything...... the engine was rebuilt with completely different rockers (std rockers to shaft mounted... same ratio supposedly), new pushrods, new lifters, same cam,... could the engine build effect IAT?.... only thing that really changed in my setup...

thougths???
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Old 02-22-2014, 12:09 PM   #10
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The fact ambient is the same, pre boost is the same, that more or less proves the sensor is reading as it should.

Now it can be affected by heat soak, but that would be apparent by high readings all the time, or when that is occurring. So maybe the runs where you seen cooler temps were not accurate, or something changed.

Of more importance than the dyno. Do temperatures on the street or track remain as before ?
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Old 02-22-2014, 03:28 PM   #11
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Quote:
Originally Posted by stevieturbo View Post
The fact ambient is the same, pre boost is the same, that more or less proves the sensor is reading as it should.

Now it can be affected by heat soak, but that would be apparent by high readings all the time, or when that is occurring. So maybe the runs where you seen cooler temps were not accurate, or something changed.

Of more importance than the dyno. Do temperatures on the street or track remain as before ?

Havent had a chance to tryout on street yet..... streets are still coated with salt and crap..... and way too many pot holes now to even think about driving it..... but yea it might be ok on the street due to the better air flow and more air pushing thru IC... but I guess the dyno temps concern me only cause of how significant the difference it.. and how much power its down...

thanks for the thoughts for sure.... was mainly worried that somehow the rebuilt engine was creating so much more heat... and something was wrong... but coolant temps look good... no oil temp gage....may look into oil temp to assure its all good there... hmm.... just a bit puzzling....
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Old 02-24-2014, 01:55 PM   #12
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Issue solved..

after trying 3 air temp sensors..... 3rd one worked good!!!!!!

also found out the rocker ratio was wrong on my rebuild.... they used 1.7 versus the 1.8 I had in it originally...... big difference!!!!
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Old 02-24-2014, 04:04 PM   #13
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So it was a faulty sensor ?
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Old 02-24-2014, 08:29 PM   #14
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So it was a faulty sensor ?
Yep.....

They had to try three to find a good one that read correctly.... also some wires leading to it were questionable.... got temps way down.... its weird that it didn't show what it would if it was grounded out or not getting the voltage.... just some random high values....

it was the last resort before..... not even sure what would be next....

I guess three times is a charm!!!!

thanks for your assistance...
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Old 02-25-2014, 07:17 AM   #15
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My concerns there would be having to try 3..

You try 3 to get one that reads correctly...or 3 to get one that reads as you wanted it to read ?

Most ecu's will default a temperature if the sensor or wiring goes open or short circuit. They are rarely random, usually user defined.
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