How much boost with this setup??

[SIR]

I am about to get my engine tunned up and the guy who will be tuning it hasn't done a lot of VR4 motors so he is not sure how hard to push it, so I am after opinions.

It is a stock VR4 motor with good compression across all cylinders.
GT3071r turbo on steam pipe manifold for rwd config
560cc Evo IX injectors + bosch 044 pump
Autronic SM4 ecu
Ls7 coils running seq ignition
Big front mount cooler

The reason I ask is the engine is going into a Improved Production car that has to run a 36mm restrictor infront of the turbo. The restrictor limits max boost pressure on a 2L to around 20psi then it quickly drops off to around 15psi. A lot of the guys run no boost controller and let the restrictor limit the pressure. I know that it should handle 15psi fine but is 20psi pushing the relationship? I do plan to build a forged bottom end when the motor goes bang but wouldn't mind getting a few goes with the stock motor first.

Will the rods be the first thing to let go?

 

[mr bender]

aslong as you have fuel and timing it will be fine.

on my setup on my starion its still a stock bottomend (vr4) i ran 18psi and made 355awhp without a sweat the tunner said i could easy run 22psi easy.
these motors a strong and if you trust the tunner and he gives it fuel and timing it will be all good!!! but since you run a 36mm restrictor it will drop off to 15 psi anyway?


if you want to see how much power it makes,
take the restrictor out, wind 20psi in it , get the dyno sheet , show it off , and then put the restrictor back in and then tune it for 15psi!:thumbsup:


and the rods will be fine , you mite spin a bearing or maybe crack a pistion if your mean to it.

 

[bazeng]

I've heard of stock motors going up to 25psi - 30psi due to the extremely low comp.

But with specs like that, just boost it up until it stops making power =)
With the restrictor, I'm sure the turbo will eventually choke at a certain point.

Most 3071's I've seen run about mid 20's psi on pump fuel..

The only other limit is your injectors besides the restrictor.

Also, what sort of wastegate is it?

If you are restricted with boost, make sure you try and make use of the SM4's boost controller. You can use it to ramp on boost alot sooner than a spring would.

Make sure you post up a graph afterwards!

 

[SIR]

Bazeng it's just an internal gate, that is what the tunner requested I will be usin a 3port boost solenoid controlled by the sm4.
It am thinking of running it 100octane e10, if the injectors don't max out.

I will let it go with boost control on dyno and see how it goes, then set it up with the controller to try and bring it on earlier

 

[The Godfather]

I am about to get my engine tunned up and the guy who will be tuning it hasn't done a lot of VR4 motors so he is not sure how hard to push it, so I am after opinions.

thats scary what you wrote ^^^

my opinion would be to take it to a place that knows these motors or at least jap cars, There has to be another place...??

if you want to get a good run out of the motor and with your restrictor issue id say keep boost at 15-16psi it will go like a rocket.

will they allow a gt3071 turbo in improved production???

 

[SIR]

thats scary what you wrote ^^^

my opinion would be to take it to a place that knows these motors or at least jap cars, There has to be another place...??

if you want to get a good run out of the motor and with your restrictor issue id say keep boost at 15-16psi it will go like a rocket.

will they allow a gt3071 turbo in improved production???

The tuner does a lot of sr20's and knows how to tune autronics with restrictors, but he doesn't know how strong the bottom ends are on vr4's. Getting someone who knows autonics and restrictors is important bit. I would think that tuning a sr20 would be similar to a 4g63 and if they are as strong as a sr20 it should be no hassles.

You can run what ever size turbo you want in improved production, as long as it is breathing through the 36mm restrictors.

 

[bazeng]

As long as he has a good ear for knock and knows what he is doing with the ecu/dyno he should be right..

But the benefit of having previous experience would be that he would have some sort of an idea with the limits. That would be the only concern. Will you be using the new knock board?

 

[rob323]

I think you will find a standard vr4 motor will eat an SR20 in the strength department.
Do you have to run a wastegate? If in fact the restrictor can control boost pressure, I imagine there would be gains to be had by not having the turbulence that a wastegate causes.

 

[blackvr]

When Steve Knight was running his Improved Production Lancer/VR4 engine here in Adelaide, he had no wastegate and it used to peak at around 25psi before the restrictor took effect and knocked the boost levels down. Steve used all stock VR4 engine components, and it was as reliable plus. Standard Vr4 pistons are pretty good . Even our gravel rally motor ran similar boost on stock pistons and that goes for a year between freshen ups !

Mike

 

[rob323]

I remember reading about Steve Knight's car in an old Zoom magazine :thumbsup:

 

[VR-4Squid]

a standard vr4 motor will eat an SR20 in the strength department.

Just quoting this for truth. Supply it with enough fuel and the right ignition timing and it'll handle all you can throw at it. Compared to an SR the vr4 4G63 has stronger rods and much lower compression, so it should allow more ignition advance than an SR without detonating.

 

[bazeng]

I've been told that the 4G's react more that SR's with timing. They seem to like it more than the SR's.

 

[Entaran]

All the rallyboys I know who run in VRC with restrictors don't even have wastegates. They just let the natural airflow restriction limit the turbo.