What kind of intake temps are you guys running at idle with the superchargers? With or without intercoolers. Mine are run mid 200s without i/c. That seems awful high to me.

 

Several factors enter into the temp at idle. What is the ambient temperature. How long has it been at Idle.
My car on a 85 degree day when I drive above 40mph will show 100 degree intake temperature when I stop it will not raise much if I turn both fans on.
A run through the gears will raise it to 110. Where is your intake located that you are getting so much heat.

 

The intake runs straight down by the radiator fan and 90s into the area where the radiator overflow tank is, under the right headlight. I'm thinking that I may need to cut an opening under the filter to get some air from under the car. The AIT sensor is located about 6" in front of the TB. As far as how long it was idling, that may have been a large factor. I have just got it going and when I noticed the high temps, it had been idling for a while. Engine temps were okay.


[Modified by Ronnie_W, 10:46 AM 8/16/2003]

 

If the hood is closed at idle underhood temps will rise unless you have some real good fans. Are you picking up air in the right wheelwell I'm trying to figure out where your inlet is. I get my intake temp from within the intake manifold my old combo ran 165 to 185 now it never goes over 110

 

When the hood is closed, the cone filter is pretty much right under the right headlight. That's the area just in front of the wheel well.

 

My intake air temp sensor is located approx 12" in front of the TB. FAST recommended this because of the IAT installed in the bottom of the intake tends to suffer from "heat soak". My inlet temps at an idle tend to range from 90° - 115°F (ambient temp dependent). After some good hard running, I will pick up between 30-40°. I think most of that is due to the fact that I am still pulling air from above the headers. I run an aftermarket intercooler and am currently considering an inlet air relocation to where the battery once set.

Aaron

 

MST-IAT (pro-version only)

This table contains coefficients that are used to estimate the intake port temperature. The coefficients are looked up from a table that is based upon intake mass airflow. For a given mass airflow a corresponding coefficient is retrieved from this table. The coefficient is then applied to the calculation.

IPT=ECT-IAT coef X( ECT-IAT )-MST coef X (ECT-MST )

WHERE

ipt=Estimated intake port temperature
ect= engine coolant tempature
mst= manifold surface temperature

The purpose of this table is to capture the effects of the various heat flow elements in the intake manifold. Sensing of the intake air at a point that is not near to where the fuel and air mix can potentially cause SUBSTANTIAL errors in the calculation of air density. Air density is proportional to air temperature.

The cylinder head temperature is at or near the coolant temperature and the intake manifold surface temperature that surrounds the incoming air is at near the under hood temperature. The temperature at the port where the air fuel mix, is something in between. In the case of small air flow's (ie idle ) the incoming air picks up much of the heat from the cylinder head while at high air flow rates the incoming air from the throttle dominates.

As the values in the table increase the measurement of intake port air temperature is more influenced by the manifold surface temperature sensor reading.

Their are sevaral other tables for futher fine tuning this but I think it points out what I have been saying all along their are major differences between the Fast and the new Gen.7 This may be part of the reason my engine idles so much smoother than it did with my old unit. That and the idle/timing compensation that adjusts the timing to help smooth the idle when the cam is causing fluctuations in the vacuum. That part the fast has at least I think the newer ones do. Dam all this technical stuff gives me a headache :seeya

PS- Aaron if you install the grill I was telling you about you won't see that big increase in temp the air flow will force the heat down and out the bottom plus lowering engine temp. I was going to install a hood scoop with a seal so when the hood was closed the engine would have to draw outside air but with my new fans and grill I don't think it would gain me much I see no temperature rise. Maybe someday I will try it. :cheers:


[Modified by black bart, 5:44 PM 8/16/2003]


[Modified by black bart, 9:19 PM 8/18/2003]

 

Ronnie since you saw those high temps after idle for some time I would assume that the fan was running and the intake was sucking hot air from the radiator. Check it while driving on the road and see what it is then.

 

Bart,
You speak of two sensors in the Accel system, where is the second located? You then reference the coolant temp sensor and the IAT sensor, but no reference to the 2nd IAT sensor (unless you were speaking of the CT and the IAT as the two sensors). FAST uses these same two, yet recommends locating in front of the TB to avoid "heat soak". Based on the inputs being processed, FAST will determine the approximate inlet air temp. And you are correct that at lower air velocities, the computer would rely more heavily upon the coolant temp than on the IAT. Even with increased velocities in a short blast, this would not be enough to pull the temp of the manifold down to the temp of the incoming air, and thus is why people speak of "heat soak".

Aaron

 

Aaron reread my post. The sensors are
1=intake air temp
2=Manifold surface temp
3=coolant temp
If you carefully read the post it explains how they work.
:cheers:

 

Bart,
Reread your post, then please explain what I have asked in my previous post.
________________________________________ _____________
"[Modified by black bart, 5:44 PM 8/16/2003][/QUOTE][QUOTE]My intake air temp sensor is located approx 12" in front of the TB. FAST recommended this because of the IAT installed in the bottom of the intake tends to suffer from "heat soak".

Aaron

That is how my old Accel Generation 6 was but my pro-version 7 has two sensors. This is what it say's in the Accel manual."
________________________________________ ________

Was your old system void of a coolant sensor or possibly an IAT? I just want to ensure that I, as well as anyone else who may read this post, am clear on what you are attempting to explain. Are you saying that Accel now has a coolant sensor and an IAT sensor, and your previous DFI system did not? What I read from your post is that Accel provides something that is different than the FAST system (FAST utilizes both the coolant temp and IAT sensor), with the FAST system being the same as your previous Gen 6 set-up. Just trying to clarify.

Aaron

 

I don't know how to make it more clear what I posted was direct from my manual. As stated above I have three sensors
Sensor #1 Intake air this is the one you keep refurring to ahead of the TB
Sensor#2 Engine coolant temperature
Sensor# 3 Manifold surface tenperature this is the one you do not have. To understand how they work is explained in post above.
Apparently you where not reading beyond the part about the two sensors like my gen6 had so I removed that. What is left is exactly what is in my Accel manual it points out how baseing fuel calculations with only air temp entering the intake and coolant temp will result in errors.


[Modified by black bart, 9:27 PM 8/18/2003]

 

Found the problem. The bypass valve was not working or working properly. I borrowed on from another set up I had around the house, rigged it to fit and now it is pumping out a lot of air at idle. The other one was barely relieving the pressure. Now I can get on with the tuning.

 

CONGRATULATIONS :thumbs:
I was :banghead: on my car for about two hours last week and it feels good when you finally figure out what the problem was. :yesnod: