Lumpy idle

[mizuno man]

Hey guys
I did a TC conversion many years ago.
Car has been sitting idle for 5 years and have decided to get it up and running with a bit more poke.

Orignal conversion involved runing the VR4 ECU.
Wide block
Machined decompressed pistons
Hi flow TD05
Vr4 Intercooler
Vr4 T/B, intake manifold, blue top 450cc injectors
Balance shafts removed.

Now I have a new GT2860 garrett turbo
BC 272 cams with ajustable casm timimg fitted and running again with VR$ ECU & MAF.

I have more to do on this thing like a HaLtech p1000 sport and additional tuning, but has anyone experienced a nice lump to thier idle in any TC conversion?

It was present when it was first built it but after a years of being driven hard I suspect a vacume leak developed and it use to go scavanging.

This lump is more like a tame buzless rotary type of lump, not a WRX bleep.

[redzone]

272's will definitely give u a lumpy idle ;)

rad's car has 272/264 and it's pretty rough..

my gemini has 290 degrees duration and sounds like a PP 13B lol

[MR Bender]

yer the 272 are pretty lumpy i have them in my car and it sounds pretty cool.

[mizuno man]

I may be wrong but isn't the lump of an engine usually created by the cam lob overlap.

I am just surprised because it is similar to the lump I use to get out my mini years ago where you have to overlap cam lobs to get max intake .

I suppose thats where the adjustable cam timing will eliminate the over lap of the cams

[WANTSOM]

The overlap causes the lumpiness. Adjusting the cam wheels can induce/reduce it too to some degree.

[Adriano]

Seems like a very unusual combo, those cams are way too big for the turbo you are running. It is a 300hp turbo with 600hp cams

[mizuno man]

Seems like a very unusual combo, those cams are way too big for the turbo you are running. It is a 300hp turbo with 600hp cams

Adriano thanks for your input and concern about the combination that I am running, but where do you get your HP numbers.

The Garrett web site indicates that @ 17psi the GT2860 will produce 370hp

The Brian Crower web site has a 4g63 with a T3 @ 22psi produced max 425hp a far cry from the 600hp your quoting.

I think this set up will be a pretty good balance but isuppose only time will tell.

I should have more info on dyno results shortly.

[Adriano]

Im basing my comments on a 2860 being a stock size sr20 turbo, which max out around 210rwkw. Ive got a 2876 which is much larger and it is rated at 440hp

Im running 272's in my gtr which is really too big for it at 850hp, but it is a different motor. 264's would have been a better choice for me.

Stock evo3 cams are good for over 240rwkw when dialled in correctly.

[thrash]

Stock evo3 cams are good for over 240rwkw when dialled in correctly.

can i derail this thread ever so slightly? are stock evo3 cams the same as vr4 cams?

[Adriano]

No, bigger, cant remember the specs exactly, but ive had plenty of vr4's making over 200rwkw on the dyno with stock cams and camwheels

[redzone]

Im basing my comments on a 2860 being a stock size sr20 turbo, which max out around 210rwkw. Ive got a 2876 which is much larger and it is rated at 440hp

Im running 272's in my gtr which is really too big for it at 850hp, but it is a different motor. 264's would have been a better choice for me.

Stock evo3 cams are good for over 240rwkw when dialled in correctly.

GT2860RS is a disco potato, T25G is an S13 SR20 turbo, S14/15 used a T28 in ball or plain bearing depending where they came from..

Disco Potato's are a little weapon of a turbo, looking at about 250kw ATW from one cranked right up.. they're only one step below a 2871R..

[Adriano]

BUt he doesnt have an rs, or does he?

[dirtygalant]

Evo 3 cams are the same as VR-4 cams as far as Mitsubishi CAPS is concerned, as the VR-4 part number has been superseded by the Evo 3 part number. The lift and duration is also the same between the two. It is the Evo 1 which has smaller lift and duration compared to the VR-4 and Evo 2/3 cams. This is comparing JDM to JDM models though, for all I know the AUDM VR-4 cams could be different again, but the JDM VR-4 cams certainly are the same specs as Evo 3.

Here are the cam specs for various 4G63s:

Inhalation lift quantity (mm)
Inspiration angle (degrees)
Exhaust lift quantity (mm)
Exhaust action angle (degrees)

RVR SSG - 8.5 252 8.5 252
Evo 1 - 8.5 252 8.5 252
RVR HSG - 9.5 252 9.5 252
Evo 2/3 - 9.5 252 9.5 252
VR4 - 9.5 252 9.5 252
AMG - 10 260 9.5 264

[greenstaz82]

ive got a pair of tomei cams in mine there 260 degree with 11.5 mil lift . its lumpy at idle and a bitch to drive a low speeds , it also comes down to the tune i think , they call it a fat idle or something when they put more fuel in at idle .

[thrash]

thanks adriano and dg :beer

back to the thread, if you have 272 cams but are running a stock vr4 ecu, that might be your problem.