Intake manifold, heat soak and performance question

[aj2ssrs]

Recently a couple threads were started and heat soak was a concern. The first thread was about Nelson Racing's X ram intake and people being worried about a huge metal intake and heat soak issues. The second thread was for a heat shield to help with heat transfer from the block to the manifold. I don't understand how heat soak at the intake manifold causes a loss of performance. Isn't timing pulled when coolant temps rise beyond a certain temp or if the MAF sensor senses high IAT's?

[Rhino79]

Correct, timing will be pulled for higher engine temp, and or for higher iat. This timing pull is what hurts performance.

[aj2ssrs]

So how does heat soak of the manifold hurt performance? IAT's are measured at the MAF located upstream of the manifold and engine temp is internal engine coolant temp. So say I'm sitting at a traffic light. I have an ADM race intake so the MAF sensor is located in the airbox way upstream of the manifold. MAF sensor is reading the IATs at 80 degrees and coolant temps are up to 195. MAF sensor adjusts air/fuel ratio for 80 degree intake temps but at the same time the metal manifold is getting heat soaked. If there is no sensor on the intake manifold itself, how does the heat soak effect performance? Just trying to figure out if the concerns of intake manifolds getting heat soaked are warranted.

[VADER SS L99]

I'm no expert but just because a sensor is not picking up the hot air does no mean you won't get less performance. I would think you will get KR from the hot air and that's bad either way you look at it.

[OVRKILL]

Making claims of power loss due to "heat soak" is pure speculation based on theory. Not saying it doesn't exist, but the only way to validate this phenomena is to have the intake in each material (plastic and alum) tested side by side, same car, same conditions, etc. Can't imagine that happening unless NRE ponies up the tooling money to mold one. Even then, I wouldn't believe anything over a single digit loss. If it were me and this intake showed sizable gains justifying the swap and actually valued this "theory", I might consider a ceramic coating. Lots of fast cars out there running aluminum intakes juuuuuust fine.

I'd focus on what the intake allows to improve downstream instead of worrying about air that might be a few degrees warmer prior to combustion, e.g., cams, heads, etc.

[JEFF75645]

Originally Posted by aj2ssrs

So how does heat soak of the manifold hurt performance? IAT's are measured at the MAF located upstream of the manifold and engine temp is internal engine coolant temp. So say I'm sitting at a traffic light. I have an ADM race intake so the MAF sensor is located in the airbox way upstream of the manifold. MAF sensor is reading the IATs at 80 degrees and coolant temps are up to 195. MAF sensor adjusts air/fuel ratio for 80 degree intake temps but at the same time the metal manifold is getting heat soaked. If there is no sensor on the intake manifold itself, how does the heat soak effect performance? Just trying to figure out if the concerns of intake manifolds getting heat soaked are warranted.

Ive asked this before and never got a clear answer.

[BlaqWhole]

Originally Posted by JEFF75645

Ive asked this before and never got a clear answer.

OVRKILL and Vader both gave some really decent answers to help you out. You have to remember, the warmer or hotter the intake manifold is, well then the more it will warm or heat the incoming air. For optimal engine performance, you want a warm engine with cold air going through it. Hotter air may cause timing to be pulled or fuel to be dumped to prevent engine damage. This all causes a loss of performance. How much heat, how much timing, how much fuel, and how much hp? Well like said before there would need to be extensive testing to know for sure. Most guys who have dyno shops can give you more detailed information. But basically, hotter air, less timing, more fuel dumped, less power. Ever notice that your car is a bit faster in 35 degree weather than it is in 95 degree weather? Cold air man.

[JEFF75645]

Hey Blaq thanks for the response. My question was geared toward something else. I totally mis read the post. My comment was geared more toward maf in the air box.

[aj2ssrs]

Originally Posted by BlaqWhole

OVRKILL and Vader both gave some really decent answers to help you out. You have to remember, the warmer or hotter the intake manifold is, well then the more it will warm or heat the incoming air. For optimal engine performance, you want a warm engine with cold air going through it. Hotter air may cause timing to be pulled or fuel to be dumped to prevent engine damage. This all causes a loss of performance. How much heat, how much timing, how much fuel, and how much hp? Well like said before there would need to be extensive testing to know for sure. Most guys who have dyno shops can give you more detailed information. But basically, hotter air, less timing, more fuel dumped, less power. Ever notice that your car is a bit faster in 35 degree weather than it is in 95 degree weather? Cold air man.

I understand the effects of air temps and performance and you're 100% right about colder air temps. In 95 degree air you take a hit in performance due to less dense air and the air/fuel ratio adjusting accordingly. My point though is take that 35 degree air temp which is measured by the MAF sensor which in turn adjusts air/fuel ratio for that temp, than heat that air up due to heat soak downstream of the sensor (in this case a huge metal intake manifold) and how does it effect performance. I think what OVRKILL says is true in that it's just speculation as to what happens performance wise. Maybe Nelson Racing could chime in. Thanks for the responses and keep them coming.

[DarkObsession]

To expound a bit on what BlaqWhole said, power isn't simply a function of the MAF/IAT sensors telling the computer what do.

Let's say we have the best CAI possible on the car. Temps going to the IAT are exactly what they are outside (say, 60 degrees).

The computer will read the MAF and the IAT and dump the appropriate amount of fuel to compensate for the air coming in.

However, if the intake is heat soaked, that incoming air will heat up a LOT before it hits the cylinder. Because the incoming air is so hot, the computer will detect pre-detonation (knock) and pull timing to save the engine.

In other words, yes, colder air gives you more power but if you are heating it up a ton anyway, the computer will pull timing resulting in less power.

In my old L67, the M90 Blower on that thing was basically a heat pump. Since GM didn't put a stock intercooler on those, the incoming air - regardless of how cold it was outside - would heat up a LOT resulting in relatively less power. Obviously, the colder it was outside the better since compressing cold air was better than hot air and obviously a supercharger was going to make more power than N/A on that engine but you get the point, I hope

So yes, it is hard to say exactly how much HP you lose due to heat soak without testing but you definitely will lose some.

[aj2ssrs]

Originally Posted by DarkObsession

To expound a bit on what BlaqWhole said, power isn't simply a function of the MAF/IAT sensors telling the computer what do.

Let's say we have the best CAI possible on the car. Temps going to the IAT are exactly what they are outside (say, 60 degrees).

The computer will read the MAF and the IAT and dump the appropriate amount of fuel to compensate for the air coming in.

However, if the intake is heat soaked, that incoming air will heat up a LOT before it hits the cylinder. Because the incoming air is so hot, the computer will detect pre-detonation (knock) and pull timing to save the engine.

In other words, yes, colder air gives you more power but if you are heating it up a ton anyway, the computer will pull timing resulting in less power.

In my old L67, the M90 Blower on that thing was basically a heat pump. Since GM didn't put a stock intercooler on those, the incoming air - regardless of how cold it was outside - would heat up a LOT resulting in relatively less power. Obviously, the colder it was outside the better since compressing cold air was better than hot air and obviously a supercharger was going to make more power than N/A on that engine but you get the point, I hope

So yes, it is hard to say exactly how much HP you lose due to heat soak without testing but you definitely will lose some.

Thanks DarkObsession. Good explanation. Highlighted in red was the part I was missing. Makes sense that that's where timing is being pulled.

[BlaqWhole]

Originally Posted by DarkObsession

To expound a bit on what BlaqWhole said, power isn't simply a function of the MAF/IAT sensors telling the computer what do.

Let's say we have the best CAI possible on the car. Temps going to the IAT are exactly what they are outside (say, 60 degrees).

The computer will read the MAF and the IAT and dump the appropriate amount of fuel to compensate for the air coming in.

However, if the intake is heat soaked, that incoming air will heat up a LOT before it hits the cylinder. Because the incoming air is so hot, the computer will detect pre-detonation (knock) and pull timing to save the engine.

In other words, yes, colder air gives you more power but if you are heating it up a ton anyway, the computer will pull timing resulting in less power.

In my old L67, the M90 Blower on that thing was basically a heat pump. Since GM didn't put a stock intercooler on those, the incoming air - regardless of how cold it was outside - would heat up a LOT resulting in relatively less power. Obviously, the colder it was outside the better since compressing cold air was better than hot air and obviously a supercharger was going to make more power than N/A on that engine but you get the point, I hope

So yes, it is hard to say exactly how much HP you lose due to heat soak without testing but you definitely will lose some.

Excellent explanation man. Thanks! I also believe the ECU uses coolant temps as a way of adjusting the air/fuel ratios. But I could be mistaken. I know that some older cars had two coolant temp sensors. One was a sensor that reported back to the gauge in the car while the other one reported to the ECU. Some cars had just one sensor that did both of those functions. If I'm not mistaken, cars still have a sensor that reads coolant temps and uses that info in the tuning. Again, I could be dead wrong. But it makes sense.