After over 24yrs of supercharging, I'm making a switch to a Turbo combination. Just ordered an FIS GTRS47696 for my 363 build. Question is for individuals who use meth injection solely instead of intercooling? I've had great success doing it on my Blown application in the AZ summer. At full boost of 20lbs my IATs were steadily in the 90 deg range. What type of IATs do turbos reach when street driving? Thanks in advance!

 

EFI or carburetor? How much boost?

If the turbo isn't undersized it could be fine. I think an intercooler is always a good idea, fox kits are inexpensive.

 

I'm running meth injection on a twin turbo big block non-intercooled. At 20PSI I can go as high as 130F on an 80+ degree day. Meth kicks in at 8PSI.

 

What's Temps while street driving

 

It's fuel injected

 

Usually 20 or so over ambient, depending on the weather and not sitting in traffic obviously.

 

So it's definitely streetable! Thank you

 

Ohh yeah, I drive it around regularly without any problems. Out of boost its totally fine, and while the IATs do come up in boost the meth has kept them to reasonable levels.

 

Pretty wide misconception here with meth injection. The temps reported by an IAT sensor are total horse $hit. Its a stationary probe that is having heat constantly pulled from it over a long period of time. It is in no way an accurate representation of your charge temps.

Cruising charge temps won't hurt ya at all as you don't make any boost cruising.

 

Huh? Then what is the correct way to measure it?

 

Water meth works.

 

Agreed. You can avoid hosing your IAT sensor down.

 

Not with a meth soaked thermocouple, that’s for sure! Water/meth works great. I use it on all my setups. It acts is more like race gas though, not a charge cooler. Esp. the tiny volumes most kits spray. There is a formula you can use to calculate actual air temps semi accurately if you are interested.

Think of it as pulling X amount of heat over Y amount of time and it makes more sense.

Your IAT probe is stationary. So say you are spraying alky for 12 seconds. The tiny surface area an IAT probes thermistor does not heat soak much. (it’s the size of a match head) So blasting it with meth for 12 straight seconds pulls a ton of heat from it. This is what your IAT gauge reads. That has nothing to do with your actual air charge temp. That is simply the temp. of the sensor tip.

Similar to carb’d E85 people thinking a frosty intake manifold means the air charge is a similar temp. The intake manifold is stationary. The entire time the engine is running its being sprayed with alcohol and having heat pulled from it over time. All this means is the manifold is “using up” ethanol’s cooling capacity before it gets to the combustion chambers. It’s basically wasting energy that would be better spent cooling the CC. You can have 300*++ charge temps with frost on your intake manifold.

You have to realize how quickly an engine consumes air and spits it out the tail pipes. The air is in and out of the engine in milliseconds. There is very little TIME for the water/meth to “pull heat” from the charge.

You can easily see the reported temps are BS on a dyno. An intercooled setup at say 15lbs reporting true 80* charge temps will make a TON more power than a water/meth kit and no IC reporting the same IAT. If the charge temps people see with water/meth were accurate, it would mean tiny amounts of water/meth are more efficient than intercoolers… which is clearly false.

 

Thanks for the reply and my apologies for my slow response. You presented a nicely detailed reply with some very interesting concepts. Here are a few thoughts I hope are not considered too argumentative. I know you understand the theory but I am repeating it in places where your perspective is different. Your quote follows in blue italic

Your IAT probe is stationary. So say you are spraying alky for 12 seconds. The tiny surface area an IAT probes thermistor does not heat soak much. (it’s the size of a match head) So blasting it with meth for 12 straight seconds pulls a ton of heat from it. This is what your IAT gauge reads. That has nothing to do with your actual air charge temp. That is simply the temp. of the sensor tip.

The phase change (evaporation) from liquid to a gas is endothermic (absorbs heat) for both water and methanol. Under the right conditions this phase change takes place 10x faster than your millisecond time frame. For all practical purposes it is almost an instantaneous cooling effect. That means the time through the engine is irrelevant. An IAT at the back of the manifold is surrounded by gas molecules, not a liquid stream. If the IAt is being wet by liquid of any kind it is in the wrong place. By the time a gas has changed from a liquid to a gas it is at its correct endothermic temp.

Similar to carb’d E85 people thinking a frosty intake manifold means the air charge is a similar temp. The intake manifold is stationary. The entire time the engine is running its being sprayed with alcohol and having heat pulled from it over time. All this means is the manifold is “using up” ethanol’s cooling capacity before it gets to the combustion chambers. It’s basically wasting energy that would be better spent cooling the CC. You can have 300*++ charge temps with frost on your intake manifold.

A manifold frosts because it is cooler than the outside air and water vapor (humidity) condenses on its surface. Heat flows in one direction only, from hot to cold. I agree the manifold is adding heat to the the fuel mix (or the mix is absorbing heat from the manifold) and the mix may not be as cold as possible but if the charge temps were 300* the manifold would be hot and not frosted because heat flows only one direction, hot to cold. In my experience the manifold frosts during idle and other low volume events when there is no boost (no compression heating). However, at the end of a run the manifold is dripping wet or completely frost free and usually hot if there was decent boost.

You can easily see the reported temps are BS on a dyno. An intercooled setup at say 15lbs reporting true 80* charge temps will make a TON more power than a water/meth kit and no IC reporting the same IAT. If the charge temps people see with water/meth were accurate, it would mean tiny amounts of water/meth are more efficient than intercoolers… which is clearly false.

Water is a loser. All it is is an octane booster (as you indicated) that smooths the flame front and may inhibit detonation. However, every water molecule displaces a fuel molecule! Taking fuel out of a motor is stealing HP. Water/meth combination will always steal power compared to a similar setup with an IC only. I agree the IC setup will produce more power but it is not because charge temps are phony. The dyno is reporting how much the water is hurting you.