Ok so this isnt my 350z but alot of the guys here really know their shiet.

I picked up a 95 s14 with an sr20det. Its got most all basic bolt on's except for cams. Guy I picked it up from said the car ran perfectly fine when he had his s-afc working. When the s-afc went out, the car started to run like shiet. When you get to 5k rpm in any gear, it simply cuts out and bogs. Tons of black smoke comes out the exhaust. My mechanic said he thinks the car may have bigger injectors, possibly Nismo 740's. Could it be that since the s-afc went out, the car is running super rich? The prev owner said the stock fuel cut off is kicking in and not letting it rev past 5k rpm. Car has a Walbro fuel pump and Z32 fuel filter. I dont have an AFR gauge so I cant say if this is the problem. Next weekend Im taking off the injectors and having them flow tested. Help please. Any ideas?

Forgot to add, the car is not tuned. I know it should be, and it will be. Currently running on stock ECU and no safc.

 

anyone?

 

have you checked the plugs?

 

So for all you know it could be running injectors that are double the size of stock injectors with the ECU using them at the rate of stock injectors? that would be a good reason for smoke and could even cause it to stumble at 5K

First things first, put stock injectors in the car or tune your ECU to work with the after market injectors.

Once you do that and things are still not right, go to step B.

 

Roger that! Yeah thats actually where Im headed to with this project. First thing is I need to find out the size of these injectors. But it does make sense that they could be double the size of stock which would cause the car to run super rich and not rev past 5k rpm due to the stock fuel cut off??

 

I doubt its fuel cut off, more likely you're adding 2-3 times more fuel into the motor with only the normal amount of air, so it could be suffocating.

 

anyone else have more ideas?

 

when its cooler outside does it run better???

 

I could spit out a lot of things, but whats the point when there's a major issue with the injector sizes/tune, get that taken care of first and go from there.

My Z ran like crap with the 600cc injectors running a 550cc base map, it was too rich, it drove fine, but as soon as I gave it gas it would get really rich and start to stumble, even on the dyno the first few pulls with the base map, the car didn't want to rev at all, it just spit smoke out. Once the injectors were dialed it the car started to run the way it was meant to run.

that was 50cc difference just think what it could be like for you, maybe 100-200-300-400cc difference in injector size trying to run a stock map....

 

Actually, I still dont know for sure that the injectors are bigger than stock/ Havent verified this yet.

Lets assume that Ive got stock 370 injectors. What would cause the car to run like this? If I give it gas slowly, maybe less than 50% throttle, it will slowly climb up to around 6 to 6.5k rpm. If I go maybe 75% - Full throttle it will start to bog around 4.5k - 5k rpm.

I'll know the size of these injectors sometime this week.

 

OK so I found out that my s14 is running on Denso 550cc injectors. This is of course on a stock ecu. Bad, I know. Would a FPR help while I get my ecu tuned? I wont be able to get it tuned until next month, for the meantime, Ive ordered a Nismo FPR.