DSMchips stage 3 questions

[talon96tsi]

hey guys,

I am about to finsh a rather large parts install on my car, and have come to the point where tuning becomes important, so ill start off by listing my mods. The Car is a 91 tsi awd 5 speed.

Ported and Clipped B16g
ported 02 and 2g Manifold
MKiv supra sidemount
Hard IC Pipes
255lph Walrbo
720cc Denso injectors
3" Turboback
NGK Plugs and Wires
Aeromotive AFPR
2g mas and 3" intake
Apexi safc-2 and Pocketlogger
i have a feeling theres more im forgetting...

Now i come to my question, I'm going to order a Stage 3 Keydiver Chip for my eprom, and it asks what the fuel pressure is set at. How do i determine this? Do i need to get the car running and then play with the fuel pressure till i feel its right? or until the car is running ok? or is there a certain pressure i should set it at from the get go?

I apologize for all the questions, but any help or answers would be GREATLY appreciated.

 

[andymoraitis]

Fuel pressure settings on the 1G's are usually set at 37-39 psi with the vaccuum line disconnected.

Hope that helps,

Andy

 

[talon96tsi]

why disconnect the vacuum line?

 

[andymoraitis]

Without getting technical, you won't get a proper reading otherwise. In truth, if you set your fuel pressure without the vacuum line removed, you'll end up with a higher pressure than what you thought, continue to overrun the FPR, run rich and lose performance.

Andy

 

[talon96tsi]

ok thanks

 

[DSM90AWD]

To get technical base fuel pressure is that which occurs at 0psi, hence why removal of the boost/vaccume line is necessary.

Note that if you have an adjustable FPR it is beneficial to set your base pressure to 42psi (the std pressue at which injectors are rated). If you stick to 37psi base, a 550cc injector will actually only flow 510cc supporting ~22 less WHP.

My Stg3 is calibrated for 42psi with 660s and 2G MAS and my fuel trims are near perfect

 

[EDT007]

42 psi with or without the vacuum line connected?

 

[DSM90AWD]

42 psi with or without the vacuum line connected?

Base = Disconnected = what you tell DSMChips

 

[dnhieu]

To get technical base fuel pressure is that which occurs at 0psi, hence why removal of the boost/vaccume line is necessary.

Note that if you have an adjustable FPR it is beneficial to set your base pressure to 42psi (the std pressue at which injectors are rated). If you stick to 37psi base, a 550cc injector will actually only flow 510cc supporting ~22 less WHP.

My Stg3 is calibrated for 42psi with 660s and 2G MAS and my fuel trims are near perfect

i have never herd of that before? how did you come up with that number? im going to be running 650cc injectors should i also set my chip to 42psi of fuel pressure?

thanks
david

 

[DSM90AWD]

i have never herd of that before? how did you come up with that number?

From RC Engineering's tech site the formula for converting flow based on changes in fuel pressure:

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im going to be running 650cc injectors should i also set my chip to 42psi of fuel pressure?

I would, it gives you that extra bit of range. Note that in the DSMChips injector selection Jeff lists specific injectors (FIC/Denso/RC..etc). Not all 650cc injectors flow the same (my Denso 660s flow 710cc) so is important you choose the right ones as each has different compensations and deadtimes.

Also note that 2Gs run 42psi Base FP stock, so Jeff's Chips have different compensation for 1Gs running 42psi vs 2Gs. The 1Gs would get an additional compensation equivelent to the extra 5psi base while the 2Gs would not

 

[andymoraitis]

Excellent info and thanks for posting the more technical side of it.

Andy

 

[dnhieu]

yes very good information. i now have to find out how much fic 650cc injectors flow and if my eprom chip is programed for the higher fuel pressure.

 

[steve]

yes very good information. i now have to find out how much fic 650cc injectors flow and if my eprom chip is programed for the higher fuel pressure.

If you didn't specify a change in base fuel pressure then the chips are usually programed for factory base. Getting your injectors flow tested is a great idea. Alot of aftermarket injectors flow all over the place so at best the chips are set up for a average injector.

Steve

 

[dnhieu]

what is the minus for having 650cc injectors and if your still using a chip that is programed for stock fuel pressure