3.6 conversion guys. What fuel pump are you using?

[Moses]

Can I stick with my SC fuel pump or do I have to spring for a 993 pump? Anybody BTDT?

[ischmitz]

Mark, your pump is fine. You don't need to change it.

The older cars use higher fuel pressure compared to the 993 engine. So your pump can develop more than enough pressure.

The fuel pressure regulator on the motor takes care of having the correct fuel pressure for the injectors.

Ingo

[Moses]

Thanks again, Ingo!

[Joe Bob]

Yup, me too....there was some concern but the stock SC pump works fine.

[k9handler]

Moses it sounds like the guys are getting you the correct info, I just mentioned it since you were having problems with the engine...but it seems you were having problem with the spark and not fuel. Good luck on the project and post some updates for us all to see.

[Bill Verburg]

The others have already answered but, yes, the high pressure CIS pump works fine. The 964/993 fuel rails have a variable rate fuel pressire regulator in them so proper pressure is maintained in the rails and injectors and the excess is bled back to the tank.

***Tip for all 964 users your injectors are really marginal, update them to some 993 injectors.***

[pbs911]

***Tip for all 964 users your injectors are really marginal, update them to some 993 injectors.***

Just when you think your done . . . . another $600 project rears its ugly head.

Bill, can you point me to any dyno numbers with the 993 injectors on the 964?

[Bill Verburg]

Just anecdotal evidence from Joel Reiser and some recent investigations of 964 injector flow rates. They're pathetically anemic.

See this thread

[ischmitz]

Originally posted by Bill Verburg
***Tip for all 964 users your injectors are really marginal, update them to some 993 injectors.***

Bill, when you upgrade to higher flowing 993 fuel injectors you also need to change the fuel mapping for the WOT maps. Otherwise the mixture would get thrown off, right?

Ingo

[Bill Verburg]

Yes, Ideally you should have a custom chip burned on a dyno. But the stock injectors are so marginal that they can benefit from reduced duty cycles of a larger injector. They are very near maxed out too much of the time. The 993 injectors are a nice upgrade.

[ischmitz]

Bill,

I understand your explanation. However, the duty cycle will only change while the DME is in closed loop operation.

Once you hit more than 2/3 throttle the WOT microswitch will take the DME into open loop. As a result your bigger injectors are not treated any different compared to the stock onces. The duty cycle will not change at all but the amount of delivered fuel will go up.

So just swapping injectors is only half the picture. You will see the lower duty cycles up to 2/3 throttle and a richer mixture under full load. Please correct me if I am wrong.

Ingo

[Bill Verburg]

You are probably right, only anacdotal comments support the statement, I have not seen this on a dyno. Perhaps it was understood that a custom chip would be used. Most of us seem to have chips anyway.