Engine/Transmission (1994 - 1998) Help with Fuel plate questions

[CNichols]

Do I need to do any Boost elbow mods or make a manual boost controller if I slide my stock plate forward?



Now Im confuesed cause Im reading of people that were pushing 19lbs stock and slid the plate forward and are now getting 27lbs with no other mods. I thought that the turbos were waste gated between 18-20 psi? And I keep getting the same answer of "more fuel = more boost" Well then How come you need a elbow if you put a comp box on a 24 valve? Im pulling my hair out trying to grasp this. HELP



I did search for quite a while (2 hours) B 4 I got fed up and had to post something. Sorry if im beating a dead horse but no other treads went over this.



thanks

Charlie

 

[FreeBMW]

the injection pump that houses the fuel plate also controls the wastegate. so when you increase fuel you also increase boost.





this was a very simple explaination..... its more complacated but that should help ya understand

 

[CNichols]

Originally posted by FreeBMW

the injection pump that houses the fuel plate also controls the wastegate. so when you increase fuel you also increase boost.





this was a very simple explaination..... its more complacated but that should help ya understand

Ok that makes sense. Thanks for your help.

 

[R.ebel]

Boost

Originally posted by FreeBMW

the injection pump that houses the fuel plate also controls the wastegate. so when you increase fuel you also increase boost.





this was a very simple explaination..... its more complacated but that should help ya understand

I have to disagree with the above statement.

The wastegate actuator receives its boost signal from the intake manifold. If the wastegate is set to open at 18 psi and is in proper working order, it will open at 18 psi regardless of the amount of fueling.

 

[FreeBMW]

Re: Boost

Originally posted by R. ebel

I have to disagree with the above statement.

The wastegate actuator receives its boost signal from the intake manifold. If the wastegate is set to open at 18 psi and is in proper working order, it will open at 18 psi regardless of the amount of fueling.

I have to disagree with your discription... heres why:



if you follow the line from the intake it goes into the back of the AFC housing then back out and between cyl 4-5 valve covers and over to the wastegate actuator on the turbo. the way it was explained to me by mark at TST was that the arm in the AFC housing moves with the cam on the fuelplate and meters the positive pressureized air from the intake going to the wastegate.

 

[R.ebel]

The AFC housing does not meter boost pressure. The AFC function is to limit the amount of pre-boost fueling in order to control the level of smoke emitted. The AFC also receives its boost signal from the intake manifold, on a stock truck the AFC is plumbed in parallel with the wastegate actuator.



If the AFC did meter boost pressure going to the wastgate then why does TST send a boost elbow with the plates that they sell?



A boost elbow artificially lowers the boost signal in the line that goes to the wastgate actuator relative to the actual manifold pressure.

 

[Joe G.]

The TST kit comes with a modified boost elbow. I would not expect the stock elbow to let the boost rise above stock regardless of where the plate was positioned. When my stock plate was pushed forward that's what I saw. No change from the boost I had before. Blocking the elbow did increase my boost. I have since installed a #5 plate with the modifed boost elbow from the kit. I get about 29 PSI. Probably could get more if I messed with the set screw in the elbow, but I think 29 is more than enough.

 

[CNichols]

Well I moved the plate last night. My buddy called Piers he told us to move the plate 60 thousands of an inch forward and either get a boost elbow or make one to limit it to 30PSI. We made a boost elbow out of a needle valve and some hose barbs. I have the valve closed all the way right now so the Waste gate is blocked off and right now im just trying to keep it under 30 PSI cause thats all piers said the stock trans would hold. Runs good Cant wait to get a real plate but that will be after a new trans.

 

[Jim Fulmer]

A Boost elbow is a nice thing to have around as they are dirt cheap, match that with a stock plate slid and a bump of the timing is a nice jump in power for little money, then do Gov Springs then a plate, then a housing or a turbo, then the transmission or clutch. . then... then



Jim