Sorry this seems a very silly question but I've noticed 'safety boost' being mentioned a few times. Let me describe my cars power delivery:

 

3k boost kicks in 4k-4.5k it goes up to 7.5psi , doesnt go off the guage or anything then the power seems to drop off quickly by 5k. Whilst the initial torque and surge is fantastic I can't help but think its running out of puff awfully fast.

 

If I increased the boost to 15psi, would it have the same amount of kick low down and would the powerband be extended closer to the redline?

 

The car was dyno'd (with catback mongoose exhaust system) at 273 bhp at the fly, or 245bhp at the wheels.. which seems a little lowish, though it runs well and stuff so I can't really complain.

 

What's the story does my car sound about right for a stocky TT?

No, it doesn't sound right. Sounds like your in safety boost. Safety boost is about 7psi, but the ECU also retards timing to make it safer and noticably reduces power.

Standard boost is around 9psi, doesn't sound like a lot more, but remember the timing is also more advanced and the car has more go....

 

You could increase boost to 15psi once you've sorted your current issue/s out and are sure the engine is in good shape. You will also need the ECU chipping to provide more fuel for the extra boost.

At 15psi these cars fly.

Your dyno result of 273 is a bit low, but if your in safety mode then it will be.

Use the search function and read into safety boost, causes, fixes etc....

Good luck.

BTW, my car is running about 15psi with supporting mods and the power is REALLY strong all the way to the limiter from about 3k.

Your power drop at 5k is again probably the retarded timing from the safety boost mode.

I don't understand though, the dyno was done about 3 years ago going by the paper and the fact it looks like it was done on a BBC computer :p ... so what's this safety boost and how do I stop it - the engine is smooth as a baby's arse and makes no funny noises nor is there any leaks :S

also there's no error codes etc. to suggest a problem

If you're getting a code 55, then have you checked for boost leaks?

don't forget its called a 300zx, not a 300z ;) :tongue:

3 years is plenty of time for a problem to arise, so forget the dyno print.

So you've done an ECU check and got a code 55 (no fault detected)???

Do a search of safety boost.

AFAIK safety boost is caused by either a fault in the det.sensor circuit (code 34) OR in the temperature sensor circuit (code 13)

Even running cold with a duff thermostat stuck open would stop it ever getting out of safety boost. I dont think that would show up on diagnostic codes either. Check your top rad hose for getting pressurised and properly hot. Also the main (big) temperature sender connector for the ecu. It could be a bad contact that is failing to tell the ecu the engine is now hot and allowed full boost.

Hmm... well my temp guage goes to mid way or so which seems about right? But if its 0 or less the temp can drop right down if i floor it, but I guess it would given the coldness of the air just now? Can I not just make it alot easier and chip the ECU to ignore any potential issues? I'm happy to check for boost leaks or possibly replace the 'cooler/hosing.

When we talk about chipping the ECU, the adjustments are to the fuel and timing maps.

This does NOT increase boost, but just prepares the car for the extra boost to keep the engine safe (stops it running lean). The boost is increased by the fitment of boost jets (cheap but crude) or boost controller (expensive,but better).

Chipping cannot make the car ignore issues and would be silly to do so anyway.

The engine must be running spot on before increasing boost. The 300zx engine is a good unit, but must be treated with respect or it will cost you dear.

It might be that your engine is actually running OK and that we are suspecting you have a problem when you don't. But based on your opening thread it sounds like you do.

Ideally you need to take the car to Zedworld or another quality 300zx specialist to check the car over & tell you the score.

Where abouts are you?

When we talk about chipping the ECU, the adjustments are to the fuel and timing maps.

This does NOT increase boost, but just prepares the car for the extra boost to keep the engine safe (stops it running lean). The boost is increased by the fitment of boost jets (cheap but crude) or boost controller (expensive,but better).

Chipping cannot make the car ignore issues and would be silly to do so anyway.

The engine must be running spot on before increasing boost. The 300zx engine is a good unit, but must be treated with respect or it will cost you dear.

It might be that your engine is actually running OK and that we are suspecting you have a problem when you don't. But based on your opening thread it sounds like you do.

Ideally you need to take the car to Zedworld or another quality 300zx specialist to check the car over & tell you the score.

Where abouts are you?

 

This is where it gets annoying - the very north tip of Scotland :boat:

 

I'm going to have to rely on my experience with other cars to get me through it :(

 

But, no it wasnt the boost I was hoping to ignore but people are saying the ecu compensates by adjusting the timing - that's what I was hoping to stop. What I don't understand is every time I've experienced a boost leak before it's been painfully obvious, the car won't rev properly once on boost, the boost level will spike and dip momentarily etc. It seems odd that it just simply drops it by a couple of psi and that's it done with.

 

But here's a question - when the boost guage only goes to 7 max how to people know if it's going higher (assuming stock boost is 9 or so) without the fitment of an aftermarket boost guage anyway :confused1: I'm simply assuming it's running to 7psi but then I don't know at which point the needle stops moving .. think I need to get a guage m'thinks

This is where it gets annoying - the very north tip of Scotland :boat:

 

I'm going to have to rely on my experience with other cars to get me through it :(

 

But, no it wasnt the boost I was hoping to ignore but people are saying the ecu compensates by adjusting the timing - that's what I was hoping to stop. What I don't understand is every time I've experienced a boost leak before it's been painfully obvious, the car won't rev properly once on boost, the boost level will spike and dip momentarily etc. It seems odd that it just simply drops it by a couple of psi and that's it done with.

 

But here's a question - when the boost guage only goes to 7 max how to people know if it's going higher (assuming stock boost is 9 or so) without the fitment of an aftermarket boost guage anyway :confused1: I'm simply assuming it's running to 7psi but then I don't know at which point the needle stops moving .. think I need to get a guage m'thinks

 

no, the Jap gauge is in mmHGx100 , and its famously unreliable (Vague) anyway.

OH! So therefore acctually I'm probably comfortably on stock boost then :) woohoo!

 

 

Crashed the car today so won't be testing boost much over the next week :p hehe

Ah dear mate, dont need anymore power in this weather! Hope your okay and the car isnt too badly damaged.

Ah no im fine sliding it round and all that, it was coming in at 5mph into my drive, no gritting and its just solid ice car just wouldnt turn or brake and a second later met wall :p