EFI Conversion, Tuning and Over Boost
 

Hi guys,
I Have rebuilt my engine after it seized no.5 conecting rood to the crank. i have added a bunch of stuff that i have picked up from this forum but am having problems tuning. if some one could lend me some advice i would appreciate it.

Rebuild
New crank shaft
One new conrod
New fly wheel and clutch
Rings, bearings, gaskets plus all the bits that usualy wear out

Mods
3.2 carrera manifold
Ported heads, new valve guides
964 NA cams
blue Printed Crank and Rods
2 x Additional front mounted oil coolers
6 x 800cc injectors
Autronic 500R ignition
3 x Dual MSD coils
Garett GT35R BBTurbo 0.7 AR
Schnell Extractors
Tial 46mm WG 0.5 bar spring
Full Bay Custom Inter Cooler
Autronic SM4 Computer

Well we had the car on the Dyno at Nerang on the Gold Coast (Australia) the tuning went ok. The engine runs smoothly how ever the engine tuner tells me that at about 5500rpm the boost begins to creep substantialy and becomes uncontrolable. so he has set a temporary RPM cut out at 5800RPM untill we can sort somthing out to dump all of that extra boost.

The car makes 300.7kW at the rear Wheels @ 5800 RPM and 620Nm of torque at 5200 RPM. The RWHP figure is well short of what to guys are achieving in the US. This concerns me, however the torque figure seems higher??

My tuner says that the US figures are always inflated for some reason. i dont know about that and dont want to start an argument there..

can any of you give me some ideas to solve my over boost problem. the exhaust pipe runs straight out of the turbo No mufler. very noisy but sounds great.

also what do you think about the out put figures on the Dyno.

see attached Graph and pictures.

general driving impressions: the performance is incredible it accelerates so quickly that you have to be careful wher you do it because you run out or road in a hurry. all the gears feel strong even 4th at 100km/s has good acceleration.
the engine is crap to drive when it is cold. the idle is eratic until the enging gets a bit of temp into it. that doesnt bother me so much as it warms up quickly. also drive ability at low RPM is a bit cranky but thats to be expected considering the other Mods..

look forward to some advice.
Alex...

Got any more pics of your wastegate on the car? Need to see the exhaust outlet tube of it.

You have a 0.5 bar spring, so do you have a waste gate controller? If so, are the parameters set correctly in the ECU?

Your driveability at low rpm should be good when it's warm. Sounds like a bit more tuning is needed.

With your setup using 964 cams, driving with cold engine shouldnt be a problem at all. Mine's smooth as silk with cold engine and idles well too. Only runs richer at at slightly higher rpm when cold

Can you post a picture of the wastegate circuit? It may be to restrictive ie too small or taken from only one back. What size is your wastegate and what brand?

Waste Gate Details
 

Guys, the Waste gate is a new Tial 46mm unit. The hose connections are 6.5mm. I am using hose to match the hose barbs on the waste gate. The Screamer pipe on the waste gate is 42mm id. The waste gate is controlled by and autronic small boost valve controller. There are no kinks in the hoses. Both hoses run from the waste gate to the controller. One of them then T's off and runs to pipe exiting the inter cooler before the throttle body. See attached pictures.

thanks for your help guys Alex..

Hello ,
If you can find out what correction factor your dyno operator was using, it will make the comparisons a lot easier..If your wastegate setup proves to be good, the turbo combination could be your problem . A .7 AR will spool very quickly and feel super, but that's a pretty small back housing for such a big engine ..., it could positively account for the boost creep , as the turbine speed will still stay high enough to produce boost creep on the top end . We use closer to a 1.0 on engines reving to 7 K and bigger on 3L plus engines reving to 8 K plus.....when using a GT35R i would look into your turbo Combination ......

Connect the wastegate direct and look again for boost creep , If it still continues and you can hear the wastegate opening , then it is your small backhousing ..

The 46mm Tial and stock are large waste gates and need a good size controlling valve. Is your's big enough?

The other thing to check is the waste gate valve parameters in the ECU.

I have just had a look on the Autronic web site and have found that they have a larger boost controler valve with 1/4" barb connectors. The connectors on mine are 1/8 NPT, the hose im using is 1/4". this could be an issue. i hope i dont have to change the exhaust housing. the Turbo was recommended to me By Ray Hall in Cairns. He is a Pro..anyway i hope so..
Alex..

Mondragon,

I have a very similar build but with a K27 HFS. I am still breaking in my engine, but I notice when I pass 5K rpm (even with no boost showing) I hit a wall and the engine seems to abruptly stop making torque. What are the symptoms you experience at 5K rpm?

Thanks,

Jim

I would bet your solenoid is just fine regarding the size of the connectors. All the solenoid is doing is regulating outside air to the top of the wastegate. Your build and mine are similar and I have not problems with the controller.

So, are you saying that you can maintain the desired boost until you get to 5800? For example, driving at 4000 rpm, go full throttle and the desired boost is nailed, then climbs again at 5800? If so, that's an exhaust wastegate circuit, not a solenoid or the wastegate itself.

Also, with your build, I would expect great drivability cold, hot and everything in between - including idle.

Jim,
The engine feels fine at 5K. Iwill have to put a boost guage on it to see what it's doing. As far as cold drive ability goes i agree it should behave like factory car however when the heads were off the engine i didnt realise that that modle engine didnt have a cylinder head temp sensor. My mechanic didnt advise me to have one machined in :banghead: so we are sensing engine temp from a cyl head temp sensor fitted to where the cold start time switch is mounted in the timing chain housing..
Alex..

I don't have a head temp sensor. I put an oil temp sensor in the breather cover on top of the engine. Seems to work fine for engine temp.