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Tomei Poncams Installed ! Hmmm power...

rev210

By rev210,
in Engines & Forced Induction

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Amaru Veteran

Amaru

Posted
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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?

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The Alchemist Collaborator

The Alchemist

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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

Sydneykid Grand Master

Sydneykid

Posted
Posted
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:

Amaru Veteran

Amaru

Posted
Posted
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

Amaru Veteran

Amaru

Posted
Posted
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.

The Alchemist Collaborator

The Alchemist

Posted
Posted

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

Amaru Veteran

Amaru

Posted
Posted

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.

The Alchemist Collaborator

The Alchemist

Posted
Posted

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

Sydneykid Grand Master

Sydneykid

Posted
Posted
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...
rev210 Grand Master

rev210

Posted
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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.

Cillham Community Regular

Cillham

Posted
Posted

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.

Ronin 09 Grand Master

Ronin 09

Posted
Posted

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

Alf Proficient

Alf

Posted
Posted

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...

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