Supercharges and VE curves (Speed Density)
Thread Starter
Melting Slicks
Joined: Aug 2000
Posts: 2,388
Likes: 42
From: Murrysville PA
Supercharges and VE curves (Speed Density)
I have been thinking about this and can't figure it out. If you have a car that is supercharged the pressure in the motor is higher than the pressure outside. The MAP sensor will show 100KPA at atmospheric pressure which is what the pressure is under WOT in an N/A motor. Now lets say that you introduce 10 pounds of boot pressure. Now the pressure is higher than atmospheric. How does the MAP sensor measure this? Is that what a 2 bar map is for? I’m trying to get an idea how this works with the VE tables only accepting values as 100 max. I’m assuming that with a 2 bar map all the values are cut in half. In other words, where in your N/A VE table if you had a value of 90, with a 2 bar map this would be 45. Is my assumption correct? If so how do the timing tables work and all the other tables that use MAP voltage for calculations? I have a few years experience with the $6E code and $8D code but all N/A applications.
Thanks,
Jason
Thanks,
Jason
Safety Car
Joined: Dec 1999
Posts: 4,691
Likes: 1
From: Framingham MA
Re: Supercharges and VE curves (89vette)
If you have a car that is supercharged the pressure in the motor is higher than the pressure outside. The MAP sensor will show 100KPA at atmospheric pressure which is what the pressure is under WOT in an N/A motor. Now lets say that you introduce 10 pounds of boot pressure. Now the pressure is higher than atmospheric. How does the MAP sensor measure this? Is that what a 2 bar map is for?
Melting Slicks
Joined: Dec 1999
Posts: 2,816
Likes: 2
From: Austin, TX
Re: Supercharges and VE curves (89vette)
I'm very interested in this as well. I found some interesting discussions on th e LT1-edit archive http://www.lt1edit.com/pipermail/lt1edit/ You can download it -- it's a huge text file of all the e-mail discussions, search for 'bar'. I was hoping it was as simple as installing a 2-bar MAP, then scaling all of the tables appropriately, but it doesn't appear to be that easy. Hopefully someone with experience will chime in here!
Safety Car
Joined: Dec 1999
Posts: 4,691
Likes: 1
From: Framingham MA
Re: Supercharges and VE curves (MarkBychowski)
On the Syclone/Typhoon ECM someone has made converted bin from a 3 bar MAP from a 2 bar, I know that the their was more than scaling of the map sensor to make it work properly. I think some of the other function are affected as the MAP sensor is used in a lot of different calculations.
Thread Starter
Melting Slicks
Joined: Aug 2000
Posts: 2,388
Likes: 42
From: Murrysville PA
Re: Supercharges and VE curves (dgoodhue)
I see how they are doing it. Its basically a tuning no no. They are reducing timing and adding fuel in the PE vs RPM table. Looks pretty easy now. I guess with intercooled motors alot less timing needs to come out. You can also reduce timing with a boost retard box.
Drifting
Joined: Feb 1999
Posts: 1,773
Likes: 33
From: Bradenton Florida
Re: Supercharges and VE curves (89vette)
I belive Shalin(blownc4) was running his 93 SC'd vette with the ECM only. Not sure what map sensor. I have heard that his car ran and drove extrtemely well.
Dennis
Dennis
