hahn ic kit installed!!!
12-04-2008, 03:10 PM
#11
Former Sponsor
Join Date: 11-15-2007
Location: Yorkville, IL
Posts: 282
I consider myself a turbo noob too, but I did a lot of learning with my 240sx project. I am hesitant to answer this question simply because it's on the fringe of me feeling like I know what I'm talking about. Take what I'm about to say with a little salt, and ANYONE feel free to correct me if I'm wrong.
We currently have a "pull through" setup. This means the MAF is before the turbo and the air is pulled through. With a BOV vented to atmosphere on a pull through setup, you're exactly right. Some of the air that was measured at the inlet of the turbo is vented before combustion when the valve opens, therefore causing your A/F ratio to run momentarily rich. This is also one reason you see alot of backfiring on some modified turbo cars.
In a blow through setup, the maf is placed after the turbo, usually on the cold side (after the IC) so that the amount of air that is entering the cylinders is measured correctly. The BOV is located before the maf, so any vented air is not measured.
Doing this requires a complete retune due to the pressure of the air passing through the maf. The Hahn kit will be recirculated for that reason. It's designed to be more of a plug and play solution, which is great for most.
We currently have a "pull through" setup. This means the MAF is before the turbo and the air is pulled through. With a BOV vented to atmosphere on a pull through setup, you're exactly right. Some of the air that was measured at the inlet of the turbo is vented before combustion when the valve opens, therefore causing your A/F ratio to run momentarily rich. This is also one reason you see alot of backfiring on some modified turbo cars.
In a blow through setup, the maf is placed after the turbo, usually on the cold side (after the IC) so that the amount of air that is entering the cylinders is measured correctly. The BOV is located before the maf, so any vented air is not measured.
Doing this requires a complete retune due to the pressure of the air passing through the maf. The Hahn kit will be recirculated for that reason. It's designed to be more of a plug and play solution, which is great for most.
Until I have considerably more knowledge about how the complex Bosch DI PCM models airflow based on this delta, we will retain the intended function of the IAT1 sensor to read incoming (ambient) air temp.
12-04-2008, 03:12 PM
#12
Former Sponsor
Join Date: 11-15-2007
Location: Yorkville, IL
Posts: 282
Very nice write up mightymouse. I have to agree with you that Hahn racecraft is first rate. It might take a little longer for them to introduce there products, but when they do they are right and make great power and you can be assured that they were throughlly tested. I am going to pick up my SS this weekend from Bill and can't hardly wait to see what kind of new goodies they have installed this time.
Now all we need is that big turbo!!!!
Now all we need is that big turbo!!!!
You are correct in that we take great pride in our testing and validation process where new products are concerned. We strive to equal OEM standards of quality and capability. Our 20 years of product development have taught us that rushing products to market is far too risky, both for our customers as well as us.
We would prefer to be best than first
P.S.: Sure was fun seeing your HHR make 305 WHP on our dyno
Last edited by SindyDix; 12-15-2009 at 12:59 PM.
12-04-2008, 07:49 PM
#13
Senior Member
Join Date: 08-28-2008
Location: Houston, Texas
Posts: 542
Oh cool! Another 300whp FWD LNF!
Bill, I was not aware of the connection between the sensors. Are the sensors themselves joined, or is it just contained in the housing with the MAF? Are there seperate connecting wires? I'm sure you know what I'm getting at. Could the sensors be seperated or the same wiring be used with aftermarket sensors? Also, does the ECU make calculations based on the delta, or the actual temperatures? If it's only the delta...
You know me, always thinking and asking questions. I don't mean to be a pest.
Bill, I was not aware of the connection between the sensors. Are the sensors themselves joined, or is it just contained in the housing with the MAF? Are there seperate connecting wires? I'm sure you know what I'm getting at. Could the sensors be seperated or the same wiring be used with aftermarket sensors? Also, does the ECU make calculations based on the delta, or the actual temperatures? If it's only the delta...
You know me, always thinking and asking questions. I don't mean to be a pest.
12-04-2008, 08:49 PM
#14
Former Sponsor
Join Date: 11-15-2007
Location: Yorkville, IL
Posts: 282
Oh cool! Another 300whp FWD LNF!
Bill, I was not aware of the connection between the sensors. Are the sensors themselves joined, or is it just contained in the housing with the MAF? Are there seperate connecting wires? I'm sure you know what I'm getting at. Could the sensors be seperated or the same wiring be used with aftermarket sensors? Also, does the ECU make calculations based on the delta, or the actual temperatures? If it's only the delta...
You know me, always thinking and asking questions. I don't mean to be a pest.
Bill, I was not aware of the connection between the sensors. Are the sensors themselves joined, or is it just contained in the housing with the MAF? Are there seperate connecting wires? I'm sure you know what I'm getting at. Could the sensors be seperated or the same wiring be used with aftermarket sensors? Also, does the ECU make calculations based on the delta, or the actual temperatures? If it's only the delta...
You know me, always thinking and asking questions. I don't mean to be a pest.
The IAT1 sensor is housed in the same casing as the MAF. A separate IAT sensor could be used, and the stock PCM wiring harness cut/spliced/extended.
As for the theory of operation, that's open for further discussion. I don't know if this is fully understood in the Bosch PCM yet.
Are you looking for some benefit other than just a louder Blow-off valve in this pursuit?
