Solving Boost Spiking On The Gt3540

[DennisRB30]

G'day guys. Nice forum you have over here.

I thought this might be a good place to ask about my new turbo I purchased for my 2JZ powered Skyline. Its a XR6 spec GT35 straight of a Typhoon.

Apparently you guys have some probs with boost control? What are the issues you guys have?

How do you solve this? Does a new actuator help? Or do I have to bore the wastegate hole out and fit a new flap?

[bcl]

What boost are you trying to run?

That turbo is setup for a large capacity engine (4 litres) that will run low boost standard (5 to 6 lb). Compared to Jap engines the Ford engine is undersquare and very torquey.

The 3540 turbo is built for this, and has a relatively big compressor compared with the turbine.

So the turbo works well on the stock Ford, spools up pretty well, and with a good spread of torque from 2000 to 5000 revs.

Your 3 litre engine will have more lag, as the gas flow will be no-where near the 4-litre Ford.

The turbo will flow enough air to provide you with over 600HP.

However, go to 14 lb or more (around 500HP) and the turbos mismatched design starts to become a problem, because the exhaust housing become a major restriction, trying to dump the gas fast enough, and boost control can become an issue.

You should then consider:

1. use a bigger swing valve

2. port the exhaust housing

3. use a stronger sprung actuator.

These are relatively easy to do by a reputable workshop.

Brian

[DennisRB30]

What boost are you trying to run?

That turbo is setup for a large capacity engine (4 litres) that will run low boost standard (5 to 6 lb). Compared to Jap engines the Ford engine is undersquare and very torquey.

The 3540 turbo is built for this, and has a relatively big compressor compared with the turbine.

So the turbo works well on the stock Ford, spools up pretty well, and with a good spread of torque from 2000 to 5000 revs.

Your 3 litre engine will have more lag, as the gas flow will be no-where near the 4-litre Ford.

The turbo will flow enough air to provide you with over 600HP.

However, go to 14 lb or more (around 500HP) and the turbos mismatched design starts to become a problem, because the exhaust housing become a major restriction, trying to dump the gas fast enough, and boost control can become an issue.

You should then consider:

1. use a bigger swing valve

2. port the exhaust housing

3. use a stronger sprung actuator.

These are relatively easy to do by a reputable workshop.

Brian

←

The GT3540 is used on 3 liter engines all the time. Its probably the most common turbo upgrade for 2JZ's, RB30's, VG30's etc. Its a great match for them, yes there will be more lag than a 4 liter, but that's the price you pay for power

In fact the compressor isn't large compared to the turbine at all for a 3 liter application. Pretty much no one orders one with a 0.5 front cover, they all use the 0.7, and a lot of people use the 0.82 turbine housing. (so that's larger fronts with smaller rears than an XR6 spec GT35)

The turbo might not be efficient on a 4 liter engine at above 14psi, but on a smaller engine the same total air flow will occur at higher boost. 380rwkw is common at around 20+psi. Quite a few 2JZs are doing this.

At the moment, I am just worried about the issues I have been hearing about the stock XR6 turbo.

What problem does the new actuator solve?

What size do they bore the wastegate out to? I plan to do it at my brothers work. We have done this job before to other turbos.

Edited 08/12/06 01:55 AM by DennisRB30

[driftpig01]

Stop don't do anymore to your car a 2j in a skyline, who did that should be shot.

There are so many good kits for the 2j, T4 if you want mild or T88 for the boost junkie.

The 34/40 is not suited to a 2j

[DennisRB30]

Stop don't do anymore to your car a 2j in a skyline,  who did that should be shot.

There are so many good kits for the 2j, T4 if you want mild or T88 for the boost junkie.

The 34/40 is not suited to a 2j

←

lol. I hope this guys isn't indicative of the mentality of the members here at XR6turbo.com?

I think I know what I am doing mate. I built it myself with no help from any workshops and it done 12.5 at 115 mph with stock turbos and ECU at its first outing, and the car was cheap to build. If you think a "34/40" is not a good match for a 2JZ you have no idea.

Thanks for the input.

[driftpig01]

The 35/40 off the T is not suited to the 2j, I guess you are changing from twin to single setup?

If you change the wheels or port the exhaust housing it will be better suited.

No offence indented there are so many options for the skyline with out putting a toyota engine in. The 2j would have to be one of the best non nissan engines you could have choosen. Got love that forged bottom end.

[Romulus]

To answer your question yes the wastegate port does get enlarged and also fitted with a larger swing valve assembly to stop overboosting. The standard port size is too small to control high boost levels. You'll see some people claiming hi boost numbers with the stock actuator, but that isn't through good programming; rather a lack of boost control. Like BCL suggested you could also upgrade the actuator to a 12psi unit to give you more boost.

Good luck with your project

Edited 08/12/06 02:53 AM by M6 XR6T

[DennisRB30]

To answer your question yes the wastegate port does get enlarged and also fitted with a larger swing valve assembly to stop overboosting. The standard port size is too small to control high boost levels. You'll see some people claiming hi boost numbers with the stock actuator, but that isn't through good programming; rather a lack of boost control. Like BCL suggested you could also upgrade the actuator to a 12psi unit to give you more boost.

Good luck with your project 

←

Cheers M6. Do you know what size they port the hole to? Do they use a whole new swing arm too? I am thinking there will be clearance probs if I try to enlarge the hole concentrically and fit a larger flap. I done this to another turbo and the flapper had a tendency to jam the hole.

Driftpig. You have absolutely NO idea what you are talking about. None.

The 2JZ does not have a forged bottom end.

The 2JZ sh*ts all over RB engines and costs half as much as an RB26. And 1/4 of the price of a built twin cam 3 liter. Plus I don't give a sh*t about brand loyalty. The engine is stock besides intercooler and exhaust and is the 5th quickest and 3rd fastest car in the R31 skyline club which has 7100 members.

The GT35 is a perfect match for the 2JZ. The only prob is the wastegate, and this prob is evident on the ford engine too. Which is why I am here, to find a solution. The GT35 has been used on sh*tloads of 3 liter engines. I chose it because of the huge success is has on the 2JZ, its been proven beyond a shadow of a doubt. There are heaps of Supra's with this turbo fitted and I have plenty of dyno charts.

http://www.supraforums.com.au/forum/attach...67&d=1151463380

[F6 UTE]

Sterling choice..

A guy that's done some work on my car ( Mick @ OVABOOST ) in Perth has a 2JZ In an LJ Torrie.

Well, he strapped 2 ( TWO ) GT35/40's to a forged 2JZ.

results, first dyno pull went 700RWHP. Running thru an auto.

Intake plenum consisted of a piece of 5" pipe with factory runners glued onto the bottom, and his own hand made extractor manifold for each turb..

NO wastegates.............................................

Turbotech in Perth do the porting you require @ $175. Get a 12Lb actuator and you're set..

You will be able to send it over and they will do everything you need.

They also do a .70 comp cover with adapter for the actuator. ( Good for top end )

I have the wastegate mod done to mine, and it's great..

edit: Just called Mick, forged bottom end, 25psi. " Still got a couple of hundred in it yet, but have to do the diff"

Controlling boost with BOV's.

Edited 08/12/06 06:23 AM by F6 UTE

[DennisRB30]

Well this turbo is on the car now and its not laggy IMO. I can get 1 bar of boost by 3500 which is fairly good.

But it is spiking at high RPM like I thought it would. It reaches around .9 bar by the redline.

I noticed that the stock actuator does not open the wastegate all the way. It only has enough travel to open it to about 45 degrees. Does a new actuator also fix this problem?