Manifold air temp for draw through turbo

[Lambo]

I'm installing a MS system on a 1981 301 V8 turbo pontiac firebird. The stock fuel system is a draw through carb setup, running a 850cfm quadrajet.

I have an IAT sensor, but from what I've been reading with a turbo setup, you want the air temp sensor downstream from the turbo. Are there any suggestions on what I should utilize for a manifold temp sensor that won't be susceptible to heat soak? In this setup the turbo exit bolts directly to the intake manifold. I've purchased a second intake manifold so that I can drill and tap it without losing too much sleep. So, I suppose I can go with any size, although 1/8 NPT would be ideal.

Any thoughts on where the ideal location for the temp sensor would be in the manifold?

Here is a clear shot of the manifold. On the right side of the manifold as you look at the pic (driver side bank), you can a see a the smaller brass plug that is filling a 1/8 NPT hole. Placing it there would be fairly simply if I can find a 1/8 NPT MAT sensor, and that location is acceptable for temp measurement.



Thanks,
Scott

[Matt Cramer]

I'm installing a MS system on a 1981 301 V8 turbo pontiac firebird. The stock fuel system is a draw through carb setup, running a 850cfm quadrajet.

I have an IAT sensor, but from what I've been reading with a turbo setup, you want the air temp sensor downstream from the turbo. Are there any suggestions on what I should utilize for a manifold temp sensor that won't be susceptible to heat soak? In this setup the turbo exit bolts directly to the intake manifold. I've purchased a second intake manifold so that I can drill and tap it without losing too much sleep. So, I suppose I can go with any size, although 1/8 NPT would be ideal.

While you could put the IAT in the manifold, I'd rather redesign this so there's an intercooler involved, and put the IAT sensor downstream of the intercooler, or even in the intercooler end tank.

Any thoughts on where the ideal location for the temp sensor would be in the manifold?

That's a contradiction in terms, but the side away from the turbo hotside is a better location.

[Lambo]

While you could put the IAT in the manifold, I'd rather redesign this so there's an intercooler involved, and put the IAT sensor downstream of the intercooler, or even in the intercooler end tank.

Yeah, an intercooler would be nice, but it would be a major redesign. The way this is setup and configured I'm kind of stuck with it, unless I make major changes. If I do that I might as well power it with something else and kick the 301 to the curb.

here is what the whole setup looks like mounted it... it's all stock.


I wanted to keep the engine configuration original, with exception to an upgraded fuel system.

With draw through an intercooler is simply not an option. Water injection is what I'll have to use for cooling the air charge.

Any thoughts on where the ideal location for the temp sensor would be in the manifold?

That's a contradiction in terms, but the side away from the turbo hotside is a better location.

What is the major downside of putting the sensor in the manifold? Is heat soak the main issue?

[fury fan]

For the rest of the folks reading at home (Matt and Lambo already know what I'm going to say):
It is not 'permissible' to use a charge-air cooler with a draw-thru system. If the cooler does its job, it will cool the charge enough that fuel drops out of suspension, especially as it pings on all teh surfaces that exist in a cooler. Fuel puddling in the cooler can result, and a backfire can have disastrous results. At a minimum it will cause nasty Tau-type fuel mixture headaches.

For the IAT location:
I could only speculate on what heat-soakign will do with a draw-thru, but FWIW I can think of a handful of V8 engines that have the IAT in the manifold. I think you could tune through it. Stainless steel has a lower coefficient of heat transfer than other metals, I don't now if mounting it in a SS fitting would help.

[Matt Cramer]

While nothing is ideal about that setup, I'd probably stick an open element IAT in that front runner with the plug in it, and use ASE to deal with heat soak.

[Lambo]

Sound like a good place to start... now I just need to find a 1/8 NPT IAT sensor.

[Lambo]

Well, I found this sensor:

http://www.t1racedevelopment.com/index. ... &Itemid=72

Sounds promising. They aren't giving them away though. Open element is a must I would assume, and it has the same resistance curve as the same as GM sensors. I wish I could find a OEM solution, but this sounds like a good one if I have to get it.

[fury fan]

Dodge Magnum engines of 92-200? use a small IAT that I believe is 1/8" NPT. There are 2 different types used over the years, you'll have to research them a bit more regarding the thread and the resistance curve. Price is a LOT better than the previous one posted.

Visit Rockauto.com:
http://www.rockauto.com/catalog/raframe ... ttype=5072
http://www.rockauto.com/catalog/raframe ... ttype=5072

[Lambo]

I checked out those dodge sensors from the mid 90s... they do have a smaller thread, open cage temp sensor. They also reside in the manifold, in a similar location as where I would put it, so I think they would work.

I send BWD a question on resistance specs for those sensors, and they actually responded which was surprise itself, but it isnt' that helpfull. The WT2000, and WT3023 have the same specs.

This is what I got:


I'm obviously going to need more specs. Can these open cage sensors be submerged in water for testing like the water temp sensors can? Somebody must have used this sensor before. It would be nice if they actually have the same specs as the GM sensor.

[jcarruthers]

What's wrong with using those specs?

With a turbo you're going to always be sucking in warm air almost from startup anyway?

[Lambo]

Well... if you say that's all I need. I haven't tuned one of these before so I guess I really don't know what I need.

What if it is only 5 degrees out though and I'm starting it? The turbo won't really be spooled up so I doubt it'll raise the temp all that much.

[Teranfirbt]

The beauty of thermistors is that the resistance is logarithmic with respect to temperature, so you can use three points and curve fit the rest. Using EasyTherm with MS I or just putting those three points into MS II is all the ECU needs to be able to measure all temperatures in the range of the sensor.

[HavocFiat]

I'm installing a MS system on a 1981 301 V8 turbo pontiac firebird. The stock fuel system is a draw through carb setup, running a 850cfm quadrajet.

I have an IAT sensor, but from what I've been reading with a turbo setup, you want the air temp sensor downstream from the turbo. Are there any suggestions on what I should utilize for a manifold temp sensor that won't be susceptible to heat soak? In this setup the turbo exit bolts directly to the intake manifold. I've purchased a second intake manifold so that I can drill and tap it without losing too much sleep. So, I suppose I can go with any size, although 1/8 NPT would be ideal.

Any thoughts on where the ideal location for the temp sensor would be in the manifold?

Here is a clear shot of the manifold. On the right side of the manifold as you look at the pic (driver side bank), you can a see a the smaller brass plug that is filling a 1/8 NPT hole. Placing it there would be fairly simply if I can find a 1/8 NPT MAT sensor, and that location is acceptable for temp measurement.



Thanks,
Scott

I am a little familiar with that set up as I used to have the 1981 10th anniversary turbo edition (went to rust heaven) . From what I remember, the carburetor is mounted on a engine coolant plenum. Therefore assuming you get the same water temp through the plenum as the engine water temp. My 1st thought was to split the system and have a simple water/alcohol mixture run through the plenum, than run a water injection pump into a small cooler and into an expansion tank. In theory, reducing the charge temp significantly (not as efficient as an intercooler). Heat soak is an issue, so I would look for a way to mount the sensor in between the plenum and carb. Then I would drill and tap the aluminum elbow that bolts into the manifold and install my temp sensor there.

See if I can re-post your picture with a note.

[Lambo]

I am a little familiar with that set up as I used to have the 1981 10th anniversary turbo edition (went to rust heaven) . From what I remember, the carburetor is mounted on a engine coolant plenum. Therefore assuming you get the same water temp through the plenum as the engine water temp. My 1st thought was to split the system and have a simple water/alcohol mixture run through the plenum, than run a water injection pump into a small cooler and into an expansion tank. In theory, reducing the charge temp significantly (not as efficient as an intercooler). Heat soak is an issue, so I would look for a way to mount the sensor in between the plenum and carb. Then I would drill and tap the aluminum elbow that bolts into the manifold and install my temp sensor there.

I'm following up on this very old thread. My project has been on the back burner for awhile, but I'm spooling back up now... so to speak.

In response to this last post, from all the advice I got, it was my understanding that I "must" place the IAT sensor post turbo, due to the extreme changes in air temp that the turbo can create. Looking at the picture above you'll see a brass plug in one of the runners on the right side. That is where I ended up placing it, which is almost exactly where it was located on the vehicle i sourced it from (a late 90's dodge 318).

Water injection will probably end up on this vehicle eventually, and it will perhaps be somewhere in the carb plenum pre-turbo, post fuel, but water injection is a debate for another day.