Jump to content
SAU Community

Recommended Posts

Got the tomei 260 in/ex + cam gears and new valve springs installed in my RB26. Inlet is set +2 and exhaust -4. The thing pulls very hard throughout the rev range but having a few problems maybe someone can help with?

When the car is started and comes up to temp, the first time you give it decent throttle it starts missfiring. It does this a few times, then it clears up and doesnt happen until you tuen the car off and start it cold again (and wait for it to come up to temp of course). This has only started happening since putting the cams in. Also when it starts missfiring you can hear the turbos surging / coming on and off boost (going woosh woosh woosh woosh). After it stops misfiring, the torque is incredible and the car performs well above any expectations I had.

Also on +2 / -4 the car has a fairly lumpy idle when warmed up... is this normal?

  • Replies 131
  • Created
  • Last Reply

Top Posters In This Topic

mine was a bit lumpy too, Amaru...all it needed with a richer AFM. I tweaked mine to 13.8 to 13.5 : 1 and its fine.

what RWKW did you get mate? I guess you;ve been reading my posts....do you have std turboes?

Mike

Got the tomei 260 in/ex + cam gears and new valve springs installed in my RB26. Inlet is set +2 and exhaust -4. The thing pulls very hard throughout the rev range but having a few problems maybe someone can help with?

When the car is started and comes up to temp, the first time you give it decent throttle it starts missfiring. It does this a few times, then it clears up and doesnt happen until you tuen the car off and start it cold again (and wait for it to come up to temp of course). This has only started happening since putting the cams in. Also when it starts missfiring you can hear the turbos surging / coming on and off boost (going woosh woosh woosh woosh). After it stops misfiring, the torque is incredible and the car performs well above any expectations I had.

Also on +2 / -4 the car has a fairly lumpy idle when warmed up... is this normal?

Genberally this is a sign of it being tuned to rich for cold run, it fowls the plugs. Once its warm you give it few rpm and the plugs are cleaned and way it goes. Two soluitions, retune the cold run a/f ratios or stick in a slight hotter set of plugs. I would go for the retune personally. It is a bugger though, because you will have to leave your car at the tuners overnight so it is cold in the morning when he tunes it.

Hope that helps:cheers:

mine was a bit lumpy too, Amaru...all it needed with a richer AFM. I tweaked mine to 13.8 to 13.5 : 1 and its fine.

what RWKW did you get mate?   I guess you;ve been reading my posts....do you have std turboes?

Mike

We havnt had it on the dyno yet, all tuning was done on road (and no it wasnt a bodgy job, we used a full professional lambda meter and detonation ears with data logging). The car has HKS GT2530's. It made 300rwkw before on a conservative tune, expecting alot more now. Im not out for outright power, just nice driveability and when it stops missfiring all I can say is the car is excellent now with nice power all through the rev range.

Just need to sort out this damn missfiring issue :P

Genberally this is a sign of it being tuned to rich for cold run, it fowls the plugs.  Once its warm you give it few rpm and the plugs are cleaned and way it goes.  Two soluitions, retune the cold run a/f ratios or stick in a slight hotter set of plugs.  I would go for the retune personally.  It is a bugger though, because you will have to leave your car at the tuners overnight so it is cold in the morning when he tunes it.

Hope that helps:cheers:

Thanks for that info will pass it on. The car has power fc, does that have specific 'cold run a/f' maps? When its cold it doesnt seem overly rich, theres no black smoke puffing out on idle etc and whilst driving (granted I can only look in the mirror) when cold (i dont rev it above 2500 - 2800rpm when its cold) I cant see any black smoke coming out.

Will stick the lambda meter up it again and take it for a drive when cold and see what the AFR's are doing I guess.

hey SK, since i have tweaked the cam timing I'm sure I can hear a whistle when I'm coming on to boost that I hadn't noticed before......I'm going to check it again this weekend, sounds like a leak of some sort but am unsure on where its coming from.

The car idles like a stockie with a 13.5:1 steady AF ratio, so I'm assuming in won't be on the inlet vacuum side. Will investigate exhuast and maybe the stock blowoff valves...can these leak air???

regards Mike

The BOV gaskets are known to leak so check that and just check all your piping. First run in my car with the cams in, come onto boost and I had the lovely whistle, checked all clamps on intercooler piping and one was slightly loose and blowing open under boost ;)

On that note, looks like we have the cold start issues and missfiring sorted.

Hi Amura & SK.....you're never gonna believe this but I took all the inlet tubing off my GTR today and removed the front alloy bend off the front turbo so I could measure the compressor wheel etc etc .....The outer hole size was 52mm with a large chamfer down to approx 43mm inducer which I believe is the standard size for a GTR comp wheel. Larger comp wheels are more like 46 or 48mm. Is this correct SK??

The previous owner said it was a steel wheeled turbine/ 360 degree bearing/ and a larger comp wheel. Guess he was mistaken...he wasn't very engine literit either :)

This means that my GTR is more within "normal" power range for the mods done I guess which is a good thing!!

Just thought I'd let you know.....

Mike

The car has power fc, does that have specific 'cold run a/f' maps?

It doesn't have "cold maps" as such, there are correction tables for how much % fuel to add according to the water temp.:)

  • 1 month later...

Ronin 09,

I had several runs when I was tuning the car with the cams and PowerFC. I only kept the last one, the others showed different power curves based on moving the cam timing around. I didn't do a dyno run when the car was stock as it would have been a waste of money, I installed the cams myself in the shed and it had a stock ecu at the time so no point tuning at that stage. Having said that the power increase was already very noticable.

I am afraid that I don't often take my cars to the dyno for a run. I am take them for fine tuning and when I do and I am looking at improving the power curve the day of the tune (to me it's all relative).

I think there might be some before and after tomei cams dyno's on the UK GTR forums from memory.

I am considering a R32/33 cam and camgear upgrade for my Rb20det redtop ECCS Motor. From what i gather, even though i have Hydraulic lifters the cam should be fine even though they come from a motor with solid lifters?

Price all up buying the cams and camgears + fitting doest sound all that pricey. Considering doing this after rb25 turbo upgarde before front mount.

cheers thanks rev210.

i'm going down the same path as you (hopefully) in Feb, but will try and get the before / after dyno on the same dyno just for comparison purposes. I don't really care what the outright figure is, just interested in seeing what the up in torque across the revs is.

Thanks

Has anyone compared the price of valve springs to the tomei ones for the rb25 vct head?. ie 256 duration in and ex .

SK: I noticed in a post u made a while ago, you said you use iskendarian valve springs, are these better quality/cheaper than tomei valve springs?.

  • 3 months later...

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

    • Increasing overlap will bring the torque down earlier (and make your idle sound sick lol). Worth a shot (if you dyno time) to experience a bit (providing you are confident your valves won't kiss your pistons). Is to just take off 5 degrees across the boosted area of the map, and then retard the exhaust cam let's say, 3 degrees at a time and then overlay all the runs with VCT on all the way and VCT off as soon as you make positive pressure. Ideally you would have a total of 6x overlays to looks at 0 exhaust & VCT off once manifold pressure is +ve 0 exhaust & VCT on all the way -5 exhaust & VCT off once manifold pressure is +ve -5 exhaust & VCT on all the way -10 exhaust & VCT off once manifold pressure is +ve -10 exhaust & VCT on all the way Just leave your O2 wideband closed loop on for all of the boost area & RPM, and hopefully there isn't too much fuel correction needed and the Haltech is fast enough to compensate (I do this, then apply the correction to the main table). Getting that overlay data should give you a good indication of what to aim for.
    • So, my main limitation here is that the car does not have an oil pressure sensor by default, just a switch. As part of my tune I bought an oil pressure sensor upgrade so I now have access to oil pressure levels and logging rather than just the boolean behaviour of the switch but this means I need to use the tuning app to display this value. So, this rules out using any other app on the iPad. The app will also flash when pressure drops which is a nice feature. I have replaced the centre screen with an Android one, which is awesome for Android Auto, but I think it might be too far away and out of my line of sight. I might add some gauges to it this weekend and just see. I guess if its just temp and oil pressure I can make them massive! 🤣  
    • This is what the look like normally. Except we only got the 2 doors locally
    • Back pressure is not really a function of the exhaust itself, but the turbine/housing. So the question/point remains valid. I would be fitting an EMAP tapping point and seeing what is going on in the exhaust manifold before committing to throwing boost at it. Flow. No intercooler is actually rated for continuous operation at any power level wrt temperatures, as they are no actually capable of shifting the required amounts of heat on a continuous basis. They get hot during a pul, then dump some of that heat into the external air (and some back into the internal air) during off load moments/periods). You probaby do need a bigger core, given the power level you're already at is somewhat above the "rating" of the cooler. Put pressure tapping points either side of the core (which possibly you already have, if you have a boost source near the compressor outlet and tapping near the throttle for existing purposes) and report on delta P across the core.   I haven't done the mass flow calculation to see where you would be sitting on the compressor map at the ~450is rwkW level we're talking here, but if you look just at the PR you're running at, which is ~2.8-2.9, then you have a really really wide swath of the compressor map to run in, and so long as you were making between about 45-75 lb/min of flow, you should have really good comp efficiency, with the ideal being betweem 55 and 65. I can't see the need to shift drastically on the map to get better results.
    • Welcome 🙂 The ER34 wheels and slight lowering suit the R33 sedan really well. I'm firmly in the 'keep it stock, at least on the outside' camp.
×
×
  • Create New...