Ok so i have a vr4 4G63T in my cc gsr, my problem is it goes well up to about the 5500rpm mark an then proceeds to die in the arse. I've got a 2.5 inch turbo back exhaust , tdo5 20g turbo running 14 psi, with a pod filter also running a haltech E6X, to me it seems like its being strangled at high rpm, im assuming it has different cams to the evo, so wondering if there is much gain in going to evo cams at all? is this common for the VR4 version of the 4G to not rev well with a standard head? or does my problem lie elsewhere? Any help or hints would be appreciated. Cheers
Cams
- Thread starter htgsr
- Start date
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BMGTZ
Grumpy old man from the school of hard knocks
I have a had couple of vr4 engines now in gsrs and they don't die at 5.5k. I also have an evo two engine in my car and that runs to 8k easy ...if your brave and merciless.
perhaps they have dropped off the std cams at those revs but still pull pretty well
I cant offer much help other than to say..check
- it "can" breath both in and out. look for crushed exhaust or a restriction in the intake. how old is the turbo and is it actually flowing well
- the tune..is right afr at those revs. is the timing right at those revs
just as a side note evo 3 and vr4 cams are pretty much the same .....E1 &2 are less aggressive so there isn't much point to a change to std evo cams
VR-4Squid
Well-Known Member
BMGTZ said:
evo 2 and 3 cams are the same as vr4 cams.
evo 1 is marginally less aggressive.
stock they make peak power at 6500rpm
Got a dyno graph you could post up?
VR-4Squid
Well-Known Member
Your boost is spiking to 16psi then dropping off to 13ish - that's why it feels like it just dies up top.
Get it to hold 16psi consistently and it will feel much much better.
What sort of boost controller are you using?
O should have mentioned that im now running a elec boost controller set at 14 psi and to be honest it didnt really make any difference( not noticeable anyway) when i put it in, when Matty tuned it it was tuned to 14 so thats what i set it at, he recomended i dont go higher without putting it on the dyno to check first
There is no restriction on intake (2&1/4 with Bigish FMIC) it seems to hold 14 right through revs but i might go somewhere quiet this wknd where i can properly check this maybe the turbo is past its hay day an not flowing enough at the top end.
The boost controller is a Messenger BC which is a pain in the arse cos its all in Japanese, fun when it comes time to change it again. :unsure:
There is no restriction on intake (2&1/4 with Bigish FMIC) it seems to hold 14 right through revs but i might go somewhere quiet this wknd where i can properly check this maybe the turbo is past its hay day an not flowing enough at the top end.
The boost controller is a Messenger BC which is a pain in the arse cos its all in Japanese, fun when it comes time to change it again. :unsure:
rob323
Don't drive it, RALLY it!
Does the VR4 motor have the cyclone intake manifold? If so, I reckon the butterflies are being held closed.
rob323
Don't drive it, RALLY it!
And is the boost bleed off due to a leaking bov? Have you pressure tested the intake to check? When my bov was leaking, not only was boost dropping from 15psi down to 7psi at redline, but it was running stupidly rich because of the afm. Are you running a map sensor or afm?
No its not a cyclone intake manifold (they have cyclone moulded into them yeh?) it just has ECI Multi on it.
No BOV on it, on the Dyno graph it just had a bleed tap so that's why it spiked to 17 then settled back down to 14ish
I havent as yet pressure tested the intake side of things, but with the proper boost controller in it seems to hold 14 ok
No BOV on it, on the Dyno graph it just had a bleed tap so that's why it spiked to 17 then settled back down to 14ish
I havent as yet pressure tested the intake side of things, but with the proper boost controller in it seems to hold 14 ok
Rockabilly
Well-Known Member
You mention the turbo might be a bit sick. The large O ring inside the comp might be a bit thin & could be bleeding off it's potential.
If you remove the serclip on the comp & try sliding it off & it comes off realy easy, a $5 new O ring will solve any comp bleed off.
Just a thought. Cheers !
If you remove the serclip on the comp & try sliding it off & it comes off realy easy, a $5 new O ring will solve any comp bleed off.
Just a thought. Cheers !
rob323
Don't drive it, RALLY it!
Pressure testing the intake will show up that o ring straight away if it's a problem.
VR-4Squid
Well-Known Member
Cheers for that ill check that this wknd
ROB323 mentioned the butterflies in this might not be opening, i just read somewhere they are controlled by the ecu?? then i read somewhere vacume, the car isnt here right now so i cant go look, as mentioned above i have a Haltech so if they are computer controlled that would explain why they not working, the vacuum one makes more sense however, so from what ive read there are 8 butterflies four open to start with then the other four come into play under load???
So from here i guess its off with the manifold clean & lube???
rob323
Don't drive it, RALLY it!
There are only 4 butterflies, one in each short runner to each cylinder.
From the factory, the butterflies are set up to close off the short runner by vacuum up to 4500 rpm, at which point, the vacuum is released from the system and the butterflies open allow both the long and short runners be utilised for top end power.
There is an actuator, on the right hand side of the intake manifold, halfway between the plenum chamber and the head, with a vacuum line going to it. It looks the same as a wastegate actuator. If you pull the vacuum line off it, hopefully you will see it move and hear a rush of air going into it. The butterflies will now be in the open position and you will lose a little bit of low down grunt but gain another 1500-2000 rpm of top end power. It will make the power delivery alot smoother and make a front wheel drive car easier to drive as well.
From the factory, the butterflies are set up to close off the short runner by vacuum up to 4500 rpm, at which point, the vacuum is released from the system and the butterflies open allow both the long and short runners be utilised for top end power.
There is an actuator, on the right hand side of the intake manifold, halfway between the plenum chamber and the head, with a vacuum line going to it. It looks the same as a wastegate actuator. If you pull the vacuum line off it, hopefully you will see it move and hear a rush of air going into it. The butterflies will now be in the open position and you will lose a little bit of low down grunt but gain another 1500-2000 rpm of top end power. It will make the power delivery alot smoother and make a front wheel drive car easier to drive as well.
RHS is in drivers side? car is back i think i can see what your talking about, it has 2 lines going to it? do i need pull them both off?
rob323
Don't drive it, RALLY it!
Sorry right hand side of intake manifold, ie. passenger side of car. One single line.
