Lots Of Boost, No Power

[IanB]

Howdy everyone

Im having a problem where my car looses power after some higher load driving. Was driving around some hills at the speed limit or less tonight, and half way up the hill (10 km or so) the car starts to loose power. It still builds boost fine, infact more then it normally would, but it just makes no power. I pulled over, the muffler was glowing slightly, the turbos were glowing rather alot, and free-revving up to about 4 - 5 k builds a few pound of boost which was quite amazing. I let the car cool for 10 mins and it was ok on the way home, it was still loosing power but the affect was lessened as it cooled. Leaving it for a few hours and its fine again until I start getting near some hills and higher load stuff.

I am thinking dead cat / exhaust obstruction but before I go to bash it out to be sure, id like to get others opinions.

What do you people think?

This problem has been ongoing for a while. The turbos died a few months ago and the car sat in my garage until recently until we bolted a brand new set of 2960R-7's on - I thought the dead turbos had been the problem, but maybe this problem caused my last set of turbos to die prematurely.

Thanks for your time

Ian

[paulr33]

my suggestions

shagged engine

shagged clutch

blown cooler pipe joiners

when the turbochargers on the RB26 fail they can and often do shag the engine as well

typically ceramic dust gets into the cylinders and kills a piston or two

so

check basic compression and health

check your clutch

check standard engine diagnostics

[bradsm87]

Sounds like running lean or a timing issue. Check afr and timing.

[IanB]

Ho Hum, the old turbos were steel wheel'd R34 N1's, the motor compression tests strong and the clutch is less then 3000 k's old os giken twinplate, so I dont think its going to be any of those problems. The timing issue is intresting but the problem is intermittent - it comes and goes based on temperature. Something worth looking at however, but the car was recently tuned and a new gates performance timing kit was put on right before the turbo went.

Also the turbo didn't blow, it just let go on the oil seals on the rear.

Also did a boost leak test on the car, that was fine.

[mad082]

the fact that it builds boost when free reving makes me think it is a timing issue. a mate of mine had a similar issue in his CA18 180sx. at times it would be fine, at other times you would be driving along and it felt like you had your foot hard on the brake. the problem started off doing it only when it was cold and as it warmed up it would come good. then it started doing it randomly until it would do it pretty much all the time. it would make 1 bar of boost by 1500rpm from the bush bearing turbo off a sr20. there was definately something wrong. it turned out to be pretty serious. a broken cam. i actually have a video of it shooting flames a foot out of the back of the exhaust just sitting there and reving the engine up to about 4000rpm repeatedly (sitting there just stomping the throttle on and off)

now your problem might not be a cam being broken, but it could be something like a dodgy CAS.

[SideWhiskers]

I also reckon it's timing. I've seen SRs on the dyno on full boost making 130whp - with turbo and manifold glowing red.

-Paul

[footsoulja33]

Just an idea, but what sort of fuel pump do you have in the car?

If its the original pump, i would put a bet on that being your problem. I have experienced a similar sort of problem to what you described in a mates 180SX. The car made full boost, made lots of noise but went no where! We ended up discovering the earthing points for the fuel pump had been very dodgily redone and was not making a good connection, hence not flowing the right amount of current to the fuel pump to maintain fuel pressure and flow. My thoughts were the car was leaning out very hard, and if you say you turbo's/manifold/muffler were glowing, then that would be a sign that the engine is running extremely lean (very very hot exhaust gas temps)

So basically, if you know your still running the standard original pump, have it check for flow and pressure. But if you have only recently put in an aftermarket pump, check all of the connections to the pump, make sure any crimped connections (ideally should be soldered) have not broken and that the right gauge wire was used on the fuel pump (speaker wire will not carry the current required) Easy one to check.

When i did my fuel setup on my race car, i went for 4mm wire thickness to make sure it would handle the current draw, and also re-worked the whole circuit (made my own, direct connection to battery, 30A relay in between)

[KiwiRS4T]

As above - sounds like lack of fuel. Whatever it is it sounds like it has the potential to kill your engine. Do you have an aftermarket ecu (pref with datalogging capability)? How are you tuning it? Sounds Like a session on the dyno would be a good investment.

[IanB]

hm, dyno time sounds like the way to go I think, but before I do i have to get the cat off and have a look, but its fairly new.

Old turbos were R34 N1's which are basically GT2860R-7's anyway so I figured the tune would be ok for a while... Time on the dyno was planned on monday anyway to check AFR's.

I dont have a timing light, one will have to be borrowed but I think I can arange this. I dont think its a dodgy CAS because it cruises fine, no random mis-fires or anything of the kind. I will do a datalog on my PFC later to see what sort of timing its hitting on the tune as well.

I dont think its a fuel supply issue due to its intermittent nature, if the fuel pump couldn't supply enough petrol it would be a constant thing. Pump is a walbro by the way.

Good suggestions however keep them coming

[GTR-32U]

Definately sounds like a timing issue to me. odd however that it comes and goes. What sort of fuel you running in it ? Sounds a lot like the timing is retarding, A classic symptom of which is the glowing exhaust manifolds.I wonder if the Knock sensors are faulty

[IanB]

Hm ok

Problems are many and varied

Cat was blocked - it was causing the immediate problem of no power. This was sorted and the car made 342 hp on the dyno however the graph was flat and then spiked hard at the end.

The exhaust cam is one tooth out which probably is what caused the last turbos to die and the cat to collapse. Unfortunately for whatever reason the bolt holding in the harmonic balancer has a stripped thread (it and a gates performance timing belt kit were put on by a workshop under 7000 k's ago) - it may be able to be saved yet however.

Will have to see what happens. Im fair sick of this thing now to be honest.

[Lazy-Bastard]

Hm ok

Problems are many and varied

Cat was blocked - it was causing the immediate problem of no power. This was sorted and the car made 342 hp on the dyno however the graph was flat and then spiked hard at the end.

The exhaust cam is one tooth out which probably is what caused the last turbos to die and the cat to collapse. Unfortunately for whatever reason the bolt holding in the harmonic balancer has a stripped thread (it and a gates performance timing belt kit were put on by a workshop under 7000 k's ago) - it may be able to be saved yet however.

Will have to see what happens. Im fair sick of this thing now to be honest.

Is it the same workshop doing the diagnosis that did the belt and turbo change?

If so, are they offering to rectify their F.ckup free of charge?