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I'm better on exhaust restriction. When my cat melted itself the other week, it drove around fine - just REALLY doughy particularly when trying to boost. Had a different note too, but you won't notice these things as you haven't experienced it "working"

Dyno without the cat/catback system connected would be my recommendation. It's very much likely your cat is farked.

Going to take my cat out today to see if it is melted or looks blocked in anyway, but not very keen on driving the car so will have to wait for my tuners dyno to be operational again. The rest of my exhaust is very high quality and very free flowing, so I can't see any restrictions there. Intake is 3" metal with no reduction in size or restrictive bends so again I can't see any issues there. I'm also suspicious of my cat so will have to wait and see.

Edited by Hanaldo
Greddy front mount, 600x300x100.

It is possible but the car drives fine, doesn't feel like it has any leaks and I can't hear anything.

I had a boost leak, it was impossible to hear or feel my boost leak. Even on the dyno with me poking my head around there is just too much other noise.

Only difference was more lag and the turbo was working its arse off to make the normal amount of boost and therefore the efficiency was down so the top end was down too. But nothing that would jump out and say boost leak.

Yours is very laggy for a 0.63 rear, so there is definitely some issue there. When I had an intake restriction it didnt change the lag, just the top of the graph was very flat similar to how yours is. I think yours has a combination of problems.

Have to remember this is a completely new setup and almost always requires some troubleshooting. The pain is that you have to get a tune for the large injectors so you really want to use the dyno time effectively.

Keep your head up and dont blame the turbo yet. Only thing worse would be to go out and spend 3k on a garrett turbo kit and then have the same issues.

I had a boost leak, it was impossible to hear or feel my boost leak. Even on the dyno with me poking my head around there is just too much other noise.

Only difference was more lag and the turbo was working its arse off to make the normal amount of boost and therefore the efficiency was down so the top end was down too. But nothing that would jump out and say boost leak.

Yours is very laggy for a 0.63 rear, so there is definitely some issue there. When I had an intake restriction it didnt change the lag, just the top of the graph was very flat similar to how yours is. I think yours has a combination of problems.

Have to remember this is a completely new setup and almost always requires some troubleshooting. The pain is that you have to get a tune for the large injectors so you really want to use the dyno time effectively.

Keep your head up and dont blame the turbo yet. Only thing worse would be to go out and spend 3k on a garrett turbo kit and then have the same issues.

Any chance you an share what methods you used to find the leak?

Going to take my cat out today to see if it is melted or looks blocked in anyway, but not very keen on driving the car so will have to wait for my tuners dyno to be operational again. The rest of my exhaust is very high quality and very free flowing, so I can't see any restrictions there. Intake is 3" metal with no reduction in size or restrictive bends so again I can't see any issues there. I'm also suspicious of my cat so will have to wait and see.

if it is the issue and it makes 50kw more itll be fine to give it a squirt in 1st gear once, bugger all load so you wont really experience any detonation etc, just give it enough of a squirt to see if it did make a difference, if so off to the tuners again.

I'm thinking melted cat is the most likely problem.

Also another thing that he mentioned, my O2 sensor was causing the car to run like crap so he has left it unplugged. Any ideas why it would run like crap with the O2 sensor plugged in but run fine with it disconnected?

No issue, if its tuned around the cruise etc it wont make a difference in fact may return better economy..

We are having a few issues with rb25's having soft valve springs... more boost introduces a weird power drop. Replace springs and bingo all good but the r34 is usually no issue and it usually happens around 280rwkw

Couple of thing that is extremely important.

1. After turbo installation do check pressure leaks ( I can supply 2x simple steel plug with a hose nipple for $50). Turbo will not perform if there are leaks.

2. Most of our turbos are installed with a 18psi high pressure actuator. by pass all boost controlling devices on test run, Boost gain from EBC based on stock actuator will cause massive boost creep.

3. Make sure the car's got a at least 3inch metal induction pipe with pod filter. Do not run those metal stuffed stock intake pipe.

4. An good exhaust system should restrict no more then 10KWs (My HKS silent power made 3KWs restrictions on a 316rwkws application). So Dyno tune with cat and exhaust dropped, (front pipe only). Do a touch up run with exhaust on after tuning, Get a better exhaust if you see a massive power drop with exhaust.

If above procedures are followed you will definitely get the desired power goal.

Also people with RB25det R33s. pay attention to those 20 years old valve springs and valves. Mine were all chewed out and worped possibly from valve float. That will act as boost leak, causing lose in power and response. Recommend stronger valve springs.

Also people with RB25det R33s. pay attention to those 20 years old valve springs and valves. Mine were all chewed out and worped possibly from valve float. That will act as boost leak, causing lose in power and response. Recommend stronger valve springs.

From what I have seen this is a common issue guys.

I think all people wanting to push more than 250rwkw reliably should consider a valve spring upgrade.

Over the past week and a bit, I've lost quite a chunk of my power. At least it feels that way, given how rarely it lets go in 2nd when I plant it....

I wonder if I'm suffering from this? :(

Over the past week and a bit, I've lost quite a chunk of my power. At least it feels that way, given how rarely it lets go in 2nd when I plant it....

I wonder if I'm suffering from this? :(

Check valves. Same happened to my car. Engine felt very strong with crisp throlle response after rebuild. That slowly went away and felt worse after each dyno run. Been told by engine builder this is due to unsealed valves, mine were all under 40%.

yeah it's probably a mix of all of the above. Either way, still feels strong, just not stupidly strong like before. Plus I'm pedantic, and I worry too much, and I suffer from automotive-hypochondria.

lol.

Check valves. Same happened to my car. Engine felt very strong with crisp throlle response after rebuild. That slowly went away and felt worse after each dyno run. Been told by engine builder this is due to unsealed valves, mine were all under 40%.

hi stao

what have you done to your head?

which parts e.g. valve springs?

cheers

simon

Well I don't want any thing that could alter the performance of a stock RB25det. So it will still be a stock head with stronger valve springs.

Well I don't want any thing that could alter the performance of a stock RB25det. So it will still be a stock head with stronger valve springs.

have you chosen a brand and type yet?

cheers

simon

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