Jump to content
SAU Community

Recommended Posts

Hi

When i was at the dyno pack a couple of days ago, we encountered (is that how i should write it..? -norwegian member) a problem with the engine.

The engine mods are:

-new exhaust manifold with ext. wastegate

-tial 38mm wastegate

-Garret GT3076R A/R 82

-Greddy 1.5mm headgasket

-HKS timing belt

-FMIC

-GTSlink ecu

-3" exhaust incl. elbow

-Nismo 555cc injectors

-walbro 250 fuel pump

This is a gen. 1 engine (1994)

The engine works fine at lower revs (got 1bar of boost at 3000rpm), but when we hit about 6700rpm the engine just looses all power. and the highest rpm we got was 6800rpm.

We checked the spark plugs, coils, a/f, boost and ignition timing. The only thing we could see was the a/f going richer from about 5000rpm, and when we got to 6700rpm it goes way to rich. tried to lean it out, change the ignition timing without any luck.

The rpm limit was set to 7500rpm, but the engine rpm was neve near that.

when driving, the engine cut feels like the car suddenly braking, there is no shooting from the exhaust or misfiring.. the engine power just disappears..

The engine has only been driven 70000km since new from nissan, and was pretty much standard before i started tuning it.

So i'm wondering if anyone has had the same problem, or if you got an idea of what the problem might be?

Hopefully i can get this sorted out.

Thanks

Stian

Edited by isijappanisi
Link to comment
https://www.sau.com.au/forums/topic/175104-rb25det-problem/
Share on other sites

Hi

When i was at the dyno pack a couple of days ago, we encountered (is that how i should write it..? -norwegian member) a problem with the engine.

The engine mods are:

-new exhaust manifold with ext. wastegate

-tial 38mm wastegate

-Garret GT3076R A/R 82

-Greddy 1.5mm headgasket

-HKS timing belt

-FMIC

-GTSlink ecu

-3" exhaust incl. elbow

-Nismo 555cc injectors

-walbro 250 fuel pump

This is a gen. 1 engine (1994)

The engine works fine at lower revs (got 1bar of boost at 3000rpm), but when we hit about 6700rpm the engine just looses all power. and the highest rpm we got was 6800rpm.

We checked the spark plugs, coils, a/f, boost and ignition timing. The only thing we could see was the a/f going richer from about 5000rpm, and when we got to 6700rpm it goes way to rich. tried to lean it out, change the ignition timing without any luck.

The rpm limit was set to 7500rpm, but the engine rpm was neve near that.

when driving, the engine cut feels like the car suddenly braking, there is no shooting from the exhaust or misfiring.. the engine power just disappears..

The engine has only been driven 70000km since new from nissan, and was pretty much standard before i started tuning it.

So i'm wondering if anyone has had the same problem, or if you got an idea of what the problem might be?

Hopefully i can get this sorted out.

Thanks

Stian

The standard ECU rev limit is 6800 on the 25, are you sure that you have raised it ok ?

Link to comment
https://www.sau.com.au/forums/topic/175104-rb25det-problem/#findComment-3209556
Share on other sites

as mentioned above in the mod list, i'm running GTSlink ecu. and the rev limiter set to 7500rpm. even tried to set at 8000rpm, but the engine still wouldn't rev over 6800rpm. can't figure out what's causing this. might be a faulty GTSlink.. but the again, if the ecu was going on rev limiter, it doesn't feel like a rev limiter, the rpm just goes slowly down and up.. not like a rev limiter..

Edited by isijappanisi
Link to comment
https://www.sau.com.au/forums/topic/175104-rb25det-problem/#findComment-3209577
Share on other sites

i was going to say afm, how you explain it hits rich then mega rich, also means possible max out of AFM, that could be one down side as you should have a relative easy 300+rwkw combo there (boost dependant) more info? have you got a dyno graph of current state afr's to power at least they should have given you that with it make sure afr to power is logged

Cheers

A

Link to comment
https://www.sau.com.au/forums/topic/175104-rb25det-problem/#findComment-3209794
Share on other sites

hi, and thank you so much for the replies. the GTSlink doesn't use afm, it's replaced with a 3bar map sensor. so that can't be the problem either.. i might get my hands on the dyno graf, try to get it scanned and posted here.

and the turbo is a Garrett GT3076R with a/r .82, ext. wastegate.

Link to comment
https://www.sau.com.au/forums/topic/175104-rb25det-problem/#findComment-3209821
Share on other sites

How much boost are you running?

Does the GTSlink only run one rev limiter? There's no soft limiter? No boost cut? No flat shift limiter?

When it hits the "rev limit" (What you're currently experiencing) is it like a miss fire?

If it's getting richer and richer, why don't you try leaning it out? ( by rich I'm assuming you're talking 10:1 or 11:1)

Link to comment
https://www.sau.com.au/forums/topic/175104-rb25det-problem/#findComment-3209878
Share on other sites

We were running only 1bar of boost, i was supposed to bring up the boost when mapping on the dyna pack, but never got that far due to the rev limit problem. as far as i know the link is only using one rev limiter. when the rev limit occurs it doesn't misfire, it only looses power, feels like braking when driving.. rev goes slowly down to about 6700rpm and up to 6800rpm again and so on.

we tried to lean it out, but the total power loss at 6800rpm was still present.

and i have checked the ignition coils, even tried coils from another skyline wich works as it should, but still the same problem with mine.

Link to comment
https://www.sau.com.au/forums/topic/175104-rb25det-problem/#findComment-3211082
Share on other sites

Are you still running standard cams and valve springs? Maybe the lifters are pumping up. As said, why dont you lean it out if its going rich, thats what tuning is.

Yes, i'm still running standard cams/valve springs. and as i have mentioned a couple of times before, we leaned it out, but the problem didn't disappear. the power curves on the dyno graph goes straight down when hitting the rev limit thing..

also thinking of the link is the problem, i have tried to contact link support to get some information.

Link to comment
https://www.sau.com.au/forums/topic/175104-rb25det-problem/#findComment-3211155
Share on other sites

Another one to look out for is running the air filter beyond its capacity . If you can temporarily tap into the inlet system just down stream of the filter with a compound gauge it would tell you for sure . Once a filter imposes a flow limit nothing you can do to the ECU rev limit wise will help . It just means that atmospheric pressure can't push enough air through the filter and you get a pressure drop in the system .

When power falls off does manifold pressure take a dive ?

Cheers A .

Link to comment
https://www.sau.com.au/forums/topic/175104-rb25det-problem/#findComment-3224870
Share on other sites

Another one to look out for is running the air filter beyond its capacity . If you can temporarily tap into the inlet system just down stream of the filter with a compound gauge it would tell you for sure . Once a filter imposes a flow limit nothing you can do to the ECU rev limit wise will help . It just means that atmospheric pressure can't push enough air through the filter and you get a pressure drop in the system .

When power falls off does manifold pressure take a dive ?

Cheers A .

got a brand new HKS "mushroomfilter", the biggest one, so airflow should not be a problem, running it straight to the turbo with 4" straight pipe.. and the MAP is steady all the way.

Link to comment
https://www.sau.com.au/forums/topic/175104-rb25det-problem/#findComment-3226830
Share on other sites

  • 9 months later...

problem solved, must have been the exhaust cam causing the whole problem. Last year when working on the engine, the exhaust cam broke in two pieces, got a used one from a friend of mine. Anyways, recently ordered and installed a new set of tomei poncams, and suddenly problem solved! I can't really figure out what the problem was with the used cam I got from my friend, can't see anything wrong with it. have you guys got any ideas? :(

Going to the dyno at the end of this month, with my new tomei poncams, greddy plenum and GT3582R turbo, hoping to get a better result than last year, hehe.. :D

Link to comment
https://www.sau.com.au/forums/topic/175104-rb25det-problem/#findComment-3796733
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Nah, if I need to fit people in a car I'll just use the Mrs car, the MX5 is perfect for what I need as a fun little sports car for fun on the street As for getting in and out of the MX5, I have no issues as I am a short arse who does lots of mobility training 🥷 If anything, I have been looking at Daihatsu Hi-Jets for a work hack, I helped one of my mates move some stuff with one recently that he picked up from Just Jap, it was a little ripper and plenty big enough for what we needed, it would also be super handy for me as I do alot of gardening, and plan on having some veggie patches and native gardens in the place I buy next year when I retire I did alot landscape gardening and growing veggies prior to my current job, and loved it, and that is a hobby that can keep me sane in my retirement, and as such, the little 300kg load capacity would be more than enough for what I need it to move around I have been looking at utes for just this purpose for a while now, and a near new 2024 Hi-Jet can be had for under $30k And I would rather look at a quirky little Hi-Jet than pretty much any other little ute, well, apart from a Brumby, I love the little Brumby, and weirdly have never owned one yet I was going to buy a heap of raffle tickets to try and win the Brumby that MCM built for Subaru Australia, but sadly I totally missed the raffle, I even filled in some form to be told when the raffle started so I could buy tickets, but to my dismay I was never contacted and found out I missed it when I was randomly googling Brumbys last year... #conspiracy  Maybe I should just buy a Brumby for a little "work hack".....LOL I use to be indecisive, but now I'm not sure
    • Well.... it's not just "de-oxygenating". If you do that you just have, most likely, ethane. So you still need to do a synthesis step to combine a number of ethanes/ethanols to make circa-8-chain hydrocarbons. And of course you don't want straight chain HCs, because n-octane actually has a negative octane rating (ie, it's worse even than the n-heptane which sets the zero on the octane scale!), so you have to do some tricky catalytic chemistry to synthesise branched HCs. That's all doable - but it doesn't come for free. And.... it starts with ethanol, which is an agricultural product, and there will almost certainly never be enough of that as a base stock to replace the liquid fuels that are in use. You really wouldn't want to be planning to be using any more ethanol for fuels than is currently already used (in E10, E85s, etc). And ideally you'd be looking to reduce such usage, as it is largely wasteful, particularly in the stupid-ole'US-of-A where the corn lobby has organised it so that it's actually primary production corn that is used to make a lot of the ethanol, not by-products and waste, like it is (mostly) elsewhere. So, what I said about needing free-ish energy probably still applies. True synth fuels would be made from H2 and CO2, in a near reversal of the combustion process. In fact, given that the H2 would be split from water first, it actually is a complete reversal of the combustion process. But...energy intensive. The human race burns something like 1 cubic MILE of crude oil, after it has been made into various fuels. Every year. That's a simply stupendous amount of energy. Just assume that the density is 900 kg/m3, and that the calorific value is 45 MJ/kg, then that is 165.9 x10^12 MJ of energy. Or more than 10^19 Joules. You get a maximum of 1 kJ/s per square meter solar radiation falling on the planet's surface, and so if you halve that for daylight, and halve it again for average weather (highly optimistic) and then take ~25% for the very best efficiency of solar panels, then you need about 85.7 billion square metres of solar panels to generate enough electricity to replace that liquid fuel energy consumption. Each panel is about 1m2. That's a rather large number of panels. We also burn about a cubic mile of coal. We also use hydroelectric power. We also use nuclear. We also use a number of other sources, both "renewable" and not. You can kind of ignore the renewable ones (except for hydro, because it will all end up getting subsumed into pumped hydro for storing other renewables, and so it won't be the standalone renewable that it originally was), so we end up needing a multiple of the ground area number that I just arrived at.
    • Corvette thread then? Don't say I didn't predict the future again. "I love the little MX5, I do, but I just want something a little easier to get in/out of, a little more cushy and some power would be nice - I miss the V8 Rumble... I found this clean red C5 for sale recently and..." I'll do you a great deal on the next step, which is one of those but you can fit people in it, too.
    • What about renewable diesel and/or gasoline? I see some projects spinning up like de-oxygenating ethanol to make drop-in compatible bio-gasoline especially in CA. I still think the future is EVs and we should've all gone full throttle on nuclear power after the 1973 oil crisis like France. Despite 15 years of work in CA to reduce the CO2 intensity of generation with renewables our electric grid is still far worse than even "low carbon" nuclear power. ICE is pretty cool when you aren't depending on the stupid thing to be practical and reliable and cheap as possible to get you to work every day. It's kind of like mechanical watches or vacuum tube amps.
    • I just rolled over "my" first 10k km in the MX5 Every time I go anywhere it always ends up in a adventure to look at houses and find some random country roads I've been on leave since early November but unfortunately need to go back to work on 19 January Luckily though I still have a fair chunk of leave left to burn until.... Not that I'm counting 😁
×
×
  • Create New...