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Discussion Starter #1
I have recently purchased an R34 fitted with HKS GT 2530 turbo's and HKS step 1 cams

On light throttle and particularly when at a steady speed the turbos start puffing against each other. This is also accompanied by a slight flicker on the boost gauge. I have the feeling that one or both of the turbo's are stalling in turn against the pressure from it's partner.

A quick lift off the throttle is enough to stop the problem for a short time, but it just doesn't feel right. I have previously experienced this on an R33 with steel turbines.

It has been suggested that the HKS balance pipe tubular exhaust manifold may help this by evening up the pressure to both turbo's.

I also wonder if there may be an efficiency / volumetric balance problem that might be helped by gas flowing and matching the volume of the turbo outlets. Motorex mentioned they gas flowed their turbo's but did not comment on the exact purpose of the exercise.

Any hints / previous experience on how to deal with this problem will be gratefully received.
 

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I have felt this a few times with different cars at least I think its the same thing... I think its the blow off valves cyclying. Is it when you are starting to go into boost ?

I have had some cars do some weird stuff when the cam timing was off - check and see if you have cam gears if they have slipped or the actual timing was off. Check and make sure its 20BTDC @ 950rpm.
 

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Discussion Starter #3
Dump Valves

Hi Motorex,

Thanks for your observations.

I have felt this a few times with different cars at least I think its the same thing... I think its the blow off valves cyclying. Is it when you are starting to go into boost ?

The problem is most obvious between .2 and .8 bar boost, it is hard to sustain boost levels higher than this and keep your licence.


I was chewing the fat with Tim at SVS about hard pipe kits and dump valves and it seemed a good idea to try the car without the dump valve ( Ahmed Bayjoo the Ford tuner has on many occasions stated his hatred of dump valves ).

I disconnected the vacuum line to the dump valves and this seems to have taken away a large part of the problem - though not all.

It may be there is some linkage with the turbo shuffle starting and the dump valves responding.

I still have a notion that they are spooling up at different rates and working against each other somehow.

You mentioned on an earlier post that you gas flow the turbo compressor outlets, I have on earlier cars gas flowed the turbine inlet from the exhaust manifold to match the ports. I was advised against gas flowing the compressor outlets as it would change the A / R ( port area / radius to the centre of the port outlet ), although I have to say the as cast look of the compressor outlet ports is not pretty.

I also want to ditch the HKS FCon V and fit an Autronic or FJO inc ecu to get some datalogging and wideband Lambda support whist at the same time allowing me to ditch the airflow meters, this does not in the short term balance my turbos or sort out the dump valves.

What do you think?
 

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Shuffling ...

Could it also be affected by the fact that a six cyliners are pumping into the turbos (or is it 3 into one turbo and 3 into the other?) so you'll get some cylinders "exhausting" and others not, so there's not an even airflow driving the turbine wheels?
 

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Stock turbos aren't steel unless it was a N1. I thought that the R34 turbos were steel but I have a few sets and I had a good look at them and they have ceramic exhaust wheels.
 

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Compressor surge

Hugh,

If you experience it at part throttle and just prior to boost threshold, then it is compressor surge.

It is not good for the turbos or the engine, but it is part and parcel of living with larger turbines. It becomes more evident if you have differences in the turbines - as no two turbos are exactly alike, one will always spool faster than the other one, the difference in this spooling will exacerbate any surge problems.

It can also be a sign that your engine is not up to scratch, as in a broken ring land, etc, on a particular cylinder will incur a loss of exhaust charge (and hence an imbalance) to one of the turbos which will translate to it spooling at a slower rate.

I'd advise that you get a compression and leak down test done (to be sure).

Mario.
 

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Turbo shuffle

Hi Hugh,
You must have the HKS stainless steel manifolds,why?because you have two turbos fighting each other.I have no idea to the reason why the manifold wasnt fitted in the first place,
maybe it was a money issue or bad advise to the previous owner?My 25/10s had the same problem because the stainless steel bellows split and while waiting for a new item from HKS I had steel plates bolted on blocking the manifold balance pipe on each turbo,this was an absolute dissaster,massive shuffle.Go down to HKS and have them set up your F-CON V or my money would be on Gary at GT-ART to sort it all out.

Kind regards & good luck,
Henry.
 

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Discussion Starter #8
Still Shuffling

Hello Henry, Guy, Mario, Joss and Motorex,

Thanks for your posts, very useful info Henry on the difference with / without the balance pipe connection.

I have since advanced my ignition and leaned off the fuel and the shuffle has reduced slightly, possible because there is less fuel burning in the exhaust.

I know they are expensive, but I think Henry and Guy are correct, the HKS manifolds must be the way to go.

Does anyone know if the standard dump valves can be rebuilt, new rubbers and possibly stiffer springs to make them slower to respond as I am sure this will also help.
 

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Custom Manifolds

Hugh,

I believe the manifold is your safest bet to solving your problem. You should know that there are many custom made manifolds out there that fit a variety of turbo set ups....just have a look at the appropriate section on Hyper Rev.
Here is a picture of one of the best I have seen for a single turbo conversion on an R34.

Regards
 

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