High Compression Motor

[JJ240]

Well finally got my motor put back together with approx. 10.5:1 compression and I can barely make the thing run decent. First tried retarding the timing a bunch but it barely ran that way. I just adjusted the throttle position sensor in hopes it would give more gas thinking the throttle was open further. This seemed to work ok, but after driving it around a couple miles to test it started hesitating bad. I Was hoping to be able to get by on stock fuel system and exhaust for awhile with the higher compression. Its starting to look like I wont even be able to drive it till I can get a JWT ecu or SAFC or something. Anyone know what JWT does to the ECU to allow you to run higher compression with it? Is it something I cant achieve with just an SAFC?

[Aries]

yes you can do the same thing with SAFC.You will need a 190lph fuel pump as well.

And if you don't have a header, that's where the hesitation is coming from on a high compression motor.

[RedShred]

I have a 10:1 SOHC.I have a header and 2.5 out.Big Cam with PnP.

I have a stock ECU and stock fuel system. I dont have any problems. In fact, I'm still alittle rich at long runs at WOT. But that I account to OEM injectors and running over 85% service for too long.

i dont know why your having so much trouble. double check everything.

[TrunkMonkey]

what did you do to get your 10.5:1 compression, and what octane fuel are you using?

-demetrius

[Rownan]

I have a 10:1 SOHC.I have a header and 2.5 out.Big Cam with PnP.

I have a stock ECU and stock fuel system. I dont have any problems. In fact, I'm still alittle rich at long runs at WOT. But that I account to OEM injectors and running over 85% service for too long.

i dont know why your having so much trouble. double check everything.

10:1 compression is wussy. Still, you even admitted previously that your engine ran crappy with a bad idle. Do you not understand that you are losing horsepower by keeping the fuel system stock?

Nissans factory fuel curves are not even efficient for the stock setup, what makes you think that they'd be efficient with a higher compression motor? And in fact with higher compression the ECU is not providing the right mixture to make the car run properly..

Timhttp://www.projectaspec.com

[Rownan]

Also I suggest backing off on the timing a significant amount. That alone could allow you to run smoothly until you can take care of the stock maps.

[Open4Cycle]

Does the KA24DE have a knock sensor? If your hesitating after retarding the ignition then your to low! Move it up to 20 degree BTD and if it pings under load then back off a couple degree until it doesn't. I would have all 93 octane in the tank untill you elliminate all the bugs. I wouldn't try the octane booster either. What made you retard the timing? Did you initially have it set to 20 BTD? What did it do to begin with?

[Rownan]

Yes the KA has a knock sensor but there is no means by which to monitor it, unless you have a techtom/afc or some other gizmo that allows you to register it. The ECU uses the knock sensor to determine what to put the timing at. For the most part it is enough for minor modifications, but when you start to up the compression, the ECU is no longer able to compensate.

FYI my ECU is tuned by JWT and they FORCE the timing at 20.

[Open4Cycle]

When you say they force your timing at 20 deg. what exactly do you mean? Do you mean it no longer has a spark advance?

[RedShred]

10:1 compression is wussy. Still, you even admitted previously that your engine ran crappy with a bad idle. Do you not understand that you are losing horsepower by keeping the fuel system stock?

????I said I have a bad idle because of the big cam. Dont judge my fuel system, you dont drive my car... I never said my car ran crappy, I said it had a crappy idle.

I told him I have 10:1 to let him know that I dont have any issues and him running 10.5:1 shouldnt be much worse... especially since I have a decent cam... When my Car gets on the cam, it runs fine apart from the richness when running WOT but that is probably due to the ****ty injectors.

Sure, I know I need a better Computer, but it works and works well.

Dont blast me... If you feel the need to be aggressive, go to Fresh Alloy as they like that kind of thing there.