Car Bogging Down-Fuel Pump Issues

[Boost King]

Recently I have had a new 800HP Bosch fuel pump installed. My car was leaning out and it was a fauly fuel pump and a fauly earthing wire. PS my car is a 96 GTST.

Prior to me replacing the pump, the car ran fine, and was sweet when cold, ie you could accelarate out of any gear at any rev, clean through the range.

Now that this new pump is on, the car is running richer. Better of course and more power, but when the car is cold, and this is after I warm it up to around 50 degrees, when you accelarate and keep under 2000 -2500 RMP its fine, as soon as boost starts coming on, the car gurgles a bit and unless you apply more throttle the car suddenly unclogs itslef and launches. But if you change gears etc, it is ok. When you are up to 60km and holding the throttle constant to maintain normal driving speed, it starts hanging back, so you give more throttle, it gurgles a bit more and hits boost.

When the car is warmed up, to 8-0 degrees, and you are cruising at 60, you can accelarate and be miles away from using boost and its ok.

These symptons sound like too much fuel when the car is cold. All the above is based on driving at 0.5 bar. If you run say 0.75 bar, its even worse. The car when it bogs down seems to be corrected by a flick in nuetral, rev it out, and keep driving. Although not the quietest cars to do this in!

My mechanics are going to look at it next week, but they already said they adjusted the Throttle position slightly, and said it may also be the Air flow meter.

Also, the dyno chart, the car made 190rear wheel kilowats and the fuel line was (AFR) did not exceed 12 nor fall below 10.5 if this means anything?

Who knows anything about this.

A car no matter what, ie new toyota for example, should be just as responsive and smooth whilst cold, or hot. There should be no difference at all. Can anyone help?

Paul:(

[Kinks]

A car should be responsive cold and hot and nissan probably had it perfectly sorted - until you put a huge pump in which is pushing far more fuel through.

See if the TPS adjustment helps. they might also be able to tweak the cold start enrichment via the temp sender so you don't get as much extra fuel when cold.

Not familiar enough with 33s to know what can be done though.

[JimX]

It sounds like also that your injectors might be a bit clogged. Try getting them cleaned and see if that helps.

I recently sold my S-AFC pending the delivery of my PowerFC, and I was expecting something similar to happen to my car when going back to the unmod'd factory ECU, because I've got a Bosch 044 pump in the tank (probably the same as yours).

But surprisingly it's been really good, and my economy hasn't even suffered. This is the evidence I would use to suggest that there might be something else affecting the problem.

Installing and tuning a S-AFC will definitely help. But I think you should also clean your injectors

Edit: Just noticed your AFR's. Not exceeding 12:1 is ok, although I think it can safely go above this at low rpm (cruising) to save fuel. 10.5:1 is too rich. Use a S-AFC or the like to bring it above 11.5 or so in upper rev ranges. 12 is optimal, but 11.5 will give you a bit of a safer mixture for summer.

[Boost King]

Thanks guys for those replys. In regards to getting the injectors cleaned, we actually tried that as well. The injectors I was told by almost every one in Adelaide stated they cannot be cleaned. The guys who said they could clean them, were puzzled when they saw them. Apparantly they are a wet style injector and cant be cleaned. Please correct if this statement is wrong.

As for the S-AFC, how much is one of these to instal and tune?

I will also try to post up my dyno chart to show what the AFM ratio is doing as the revs increase.

Thanks allot for the info.

PS: I also had my computer swapped for another stocky and even had all the fuel lines pumped to remove any crap etcetc. Didn't make a difference.

[JimX]

I've never heard of an injector that can't be cleaned, but there's a first time for everything Just try a bottle of that injector cleaner stuff you buy in spare parts shops then. I find Nulon to be the best.

You can pick up an S-AFC for around $300-350 second hand, there's usually a few guys in these forums selling theirs. Or you can try Ebay, but the delay in buying is longer and the prices are usually higher due to non-Skyline people also wanting to buy them. Installing should take around an hour (so whatever your local workshop's hourly rate is) and dyno tuning around maybe $100-$150.

So budget for around $600 or less all-up.

Edit: You can install the S-AFC yourself if you're handy with a soldering iron, I did mine myself.

[predator]

Sounds pretty much the exact same issue i have been having a bit....see below:

http://www.skylinesaustralia.com/forums/sh...&threadid=27375

i changed my pump a while back. But it does seem to have resolved itself slightly with different fuel and its not really that bad. I have an S-AFC, i think it just needs a proper mixture adjustment and all should be fine. Just bumping down a few points where it was occuring has helped. I wish i had a proper A/F meter then i could do it properly.

Running on boost its a caged animal and running the best it ever has, and that problem only seems a bit intermittant so really not too fussed. Doesn't seem quite as pronounced as yours though boost king.

[Boost King]

Thanks for the replies.

I read the links supplied and it raises a interesting point about how dyno tuners tune the car on full throttle, and you cant exactly drive around on full throttle all the time.

I will take many of these points to my tuner next week and fill you all in on how it went.

:uh-huh:

[JimX]

Tuners don't tune it on full throttle, they run it up and down the rev range and see where the AFR's are all throughout, and adjust each load point as necessary. What's hard to do on a dyno though is simulate driving it down the road. ie, at 100kph the car is going to have more air rushing into the intake than at 5kph. That's why they usually put a bigass fan at the front of the car, to try making the airflow a bit more realistic (and to keep things cool)

[Boost King]

That is interesting. I once had my HQ holden dynotuned and they put the big fan in front of it because it loved running hot, so it was more to cool it down.

These nissans can be banged around all day and still stay at 80 degrees.