[DorkMissile]

Originally Posted by Tim M

Heater: I did not track the temps on the autobahn, but may in the future. On the track it hit 163 degrees on the IAT...long high rpm uphill accel in 4th and 5th gear. It was still making more thrust than I could use. I plan to stick with the octane booster - only required occasionally for typical driving I do.

163 degrees while it is moving? That's hot.

I do a event here in Minnesota called PowerCruise in the summer at Brainerd International Raceway. It is a 4.5 mile road coarse and when it is all said and done, it can be a hour long sprint on the track at full effort in humid August weather (high 90s)

As a point of perspective, running meth injection, lap after lap, I will not see a IAT any higher than 90 degrees (and that is on the section of the track where you can't be in boost for very long, so the meth system is not spraying)

I can come onto the front strait at 90mph, run almost 3/4 of a mile wide open and let off at the end of the strait (at 175) and the IATs are in the mid 60 degree range. Did it for three days, 800 miles worth.

I tore that engine down over the winter to do forged internals (it was previously just a all stock LT1 with LT4 fueling and 10lbs of boost from a Novi 1500) and everything inside the engine looked new.


Just be careful - the LT4 blower is known to bleed some oil once they have a ton of miles on them or have been pulleyd - if you get any oil inside the blower and it gets blown into the engine you have a very high risk of causing a lot of detonation really fast

[Tim M]

DorkMissile: Your experience is a good data point! Can't argue with real world example.

What is normal for IATs on an OEM LT4? My two 'ok' laps, the IATs were always over 135 and generally in the 145 range. I can understand lowering them for engine preservation, not sure it is worth the complexity/weight/expense of an methanol install. The car already makes more power than I can employ on the track. :-)

I don't plan to change the pulleys in the future (at least overseas). Unless things go south, likely only updates might be air intake, TB, and porting the blower. A project for next winter. I've got a long way to go until I'm comfortable - a good problem to have!

[ss2fast4u]

Originally Posted by 1LEornothing

I knew someone out there has, have you rung it out at 150+ like Tim has? He claims it only happens on that tall 5th gear but otherwise fine 1st 2and 3rd and 4th.

yea havent done any 150+ runs. Honestly probably wont be often just due to no where to do it. have me wondering about IAT's.



How are you guys hooking up monitors for that?

[DorkMissile]

Originally Posted by Tim M

DorkMissile: Your experience is a good data point! Can't argue with real world example.

What is normal for IATs on an OEM LT4? My two 'ok' laps, the IATs were always over 135 and generally in the 145 range. I can understand lowering them for engine preservation, not sure it is worth the complexity/weight/expense of an methanol install. The car already makes more power than I can employ on the track. :-)

I don't plan to change the pulleys in the future (at least overseas). Unless things go south, likely only updates might be air intake, TB, and porting the blower. A project for next winter. I've got a long way to go until I'm comfortable - a good problem to have!

Well the engine management is not really "complicated", but it has a lot of things going on all at once.

For example - talking about "KR" - or Knock Retard. This system is actually audible, and works by detecting the frequencies in which detonation is happening. Most people observe the logs and as long as the KR shows that the ECU is not pulling timing, that the tune is stable. But consider "KR" is the safety net. It is the last resort.

The tune is monitoring multiple tables all at once. Of which are the MAF (air volume), MAP (pressure in the intake), water temp, and intake temp. All of which have tables that will pull timing as things steer towards the bad side of things.

So the tune call be pulling timing for many other reasons outside of the KR

Looking at a log file from that weekend at BIR, after 10 minutes of running, at the end of the strait (this was the last lap of a 14 minute session) - weather was in the low 90s, 70% humidity, IAT was 72 degrees (was 102 at the start of the strait)

looking at my tune - at the moment of peak boost (155kpa) my MAF is at 1.10g (near max on the sensor) and my IAT was 72 degrees. With those numbers, it was adding timing (about 1/2 of a degree). If my IATs were at 133deg - it would be pulling 4 degrees. At 154, pulling 7 degrees. AT 190, pulling 10. My spark advance was near 20 degrees at the time - if I was at 154IAT, it would be all the way down to 13.

One degree of timing (roughly) = 14hp - and running prolonged under efficient timing settings can lead to a lot of overheating. I have several friends with LSA powered CTS-Vs that only can run 2-3 laps and have to pull off as they start pulling a lot of timing because of the IATs, which pulls timing, which adds a lot of engine heat and their engine oil temps start to shoot up.

I could run until I ran out of fuel or tires.

The LT4 blower is a nice unit, but it isn't setup with a lot of cooling. It was kind of meant to used to rip from light to light, so the intercooler setup gets overwhelmed easily. Meth would be the cheapest, easiest to install, and lightest weight way to drop your IATs 60 - 70 degrees.

[KingLT1]

If your IAT sensor isn't plumbed into the intake manifold similar to a PD setup that has the sensor in the lower portion of the supercharger manifold, then you can not compare temps. The IAT spark tables are going to be adjusted to account for this. This is what often gets confused between different FI setups.

[DorkMissile]

Originally Posted by KingLT1

If your IAT sensor isn't plumbed into the intake manifold similar to a PD setup that has the sensor in the lower portion of the supercharger manifold, then you can not compare temps. The IAT spark tables are going to be adjusted to account for this. This is what often gets confused between different FI setups.

For reference - mine is about 2" behind the throttle body on the stock LT1 intake

[KingLT1]

Mine is clear at the back down by #7 intake port. My tune is set so it doesn't pull any timing until 154 degrees which is only -1 degree, then -3 @ 174. I have never seen numbers anywhere near this hot yet. Either way I am not saying you are wrong and I do agree with what you are saying to the OP. I just mean don't get too caught up in cross comparing IAT's. I would still expect a Centri to have lower IAT's.

[DorkMissile]

Saw my tuner today - asked his thoughts, and what he could say is that on long runs, the LT4 SC would really make a lot of heat - just not a lot of "brick" inside it.

When asking about PD vs Centrifugal tunes and talking about sensor placement - he felt there will be temp variation based on the heat soak of the aluminum on the Eaton would eventually not go away unless it was running meth. He made a good point - as he has seen my logs - my IATs are all over the place in a short amount of time, where as the PD setup will take a lot longer to drop temps as all that aluminum is hot.

As far as the OP goes - he would subscribe going to a Edelbrock or Maggie as they tend to be better cooling, but if a OEM solution is needed for emissions - to look at a LT5 S/C since GMP will sell them separate from the crate engines now.

[KingLT1]

Wasn't the ZL1 one of the fastest if not the fastest road course car in it's class? Sure it may create some heat but at stock boost levels it will be fine. If anything just lower boost, then run a flex sensor and E85. Op already has LT4 fueling and it will handle E85 @ 6-7psi. Manual LT1 cars will make 600whp on E at that boost level.

[Tim M]

Well, appreciate the input folks although the thread got a bit off track. ;-)

I don't believe my combination is that far from an LT4 - quite happy with the performance. E fuel is not readily available here. I did go with the LT4 due to inspection challenges, light weight, and OEM reliability.

Even on the street, the PD blower really excels. Drive the car all day below 2000 rpm or even lower with spritely performance. This was not the case without the blower. Admittedly, I tend to dawdle on the street in high gears.

Amazing 650 hp - modern technology...

[wnta1ss]

Originally Posted by Tim M

I don't believe my combination is that far from an LT4 - quite happy with the performance. E fuel is not readily available here. I did go with the LT4 due to inspection challenges, light weight, and OEM reliability.

I would think that you actually have more power than a stock ZL1 right now. Reason being, you are spinning the blower just as fast, but your engine has a higher compression ratio.

[Tim M]

Originally Posted by wnta1ss

I would think that you actually have more power than a stock ZL1 right now. Reason being, you are spinning the blower just as fast, but your engine has a higher compression ratio.

Do not disagree...my comment was toward the IATs...ZL1 is reliable on the track with likely similar IATs. Although my timing may be not be as advanced on the lower compression/forged piston Chevrolet offering.

Should mention too that I found I could pull a gear higher in some corners - nice option.

[KingLT1]

Originally Posted by Tim M

Well, appreciate the input folks although the thread got a bit off track. ;-)

I don't believe my combination is that far from an LT4 - quite happy with the performance. E fuel is not readily available here. I did go with the LT4 due to inspection challenges, light weight, and OEM reliability.

Even on the street, the PD blower really excels. Drive the car all day below 2000 rpm or even lower with spritely performance. This was not the case without the blower. Admittedly, I tend to dawdle on the street in high gears.

Amazing 650 hp - modern technology...

I agree with Wanta1SS that you are above stock ZL1 power. Normally LT1's only need about 7psi to make what the ZL1 does @ stock boost due to the compression difference. That is why I was saying if you were concerned with IAT, you could lower the boost, raise the octane, increase the timing and make the same if not more power with less heat.