Subaru Group N Rally car that keeps on breaking ringlands

[Martin]

Ben,

Thanks for your input. The car will be re dyno`d and i will keep in mind all the things that have been mentioned.
I will reply on this post to let people know what happened and also the Dyno graph if i can.


I will post the pictures of the failed parts ASAP. Any input from anybody will be appreciated.

Thanks

Martin

[Ben-S]

I doubt it will help you but we installed an electronic wastegate actuator (not boost controller) so that we could fully open the wastegate when the restrictor was choked and we couldnt make boost to act on the wastegate spring this helps top end considerably, not to mention lowering egts and back pressure. Not sure this is even legal in group n.

[msgofast]

Martin,

I do a lot with restrictor subi's, you need to close up the comp on air temp for timing, dyno run the air temp could start at 20degs and be 50 at the end of the run, so adding timing to low rpm and then on a stage it can go up and be over the limit. The ring lands breaking is very common on the cast pistons on the twin scrolls if not tuned right, also look at running .8 for 200kp and .77 above to 250 and above at .76, it will reduce lag, keep the pistons together, and peak torque at full boost will go up, VF turbo is not a happy turbo pushing big boost with leaner AFR like other turbo engines, egt's go up, pistons temps go up, ring lands break.

Run air temp comp at 0 for 20degs and then -1 deg for every 10degs AT on 120kpa and up, also look at your cams map, more power in that, also boost map would be better with a 3d map with TPS varrying boost, makes it easier to drive, less cooking the brakes left foot braking, also put 2% fuel in #2 on positive pressure.

Cheers
Michael

[Martin]

I doubt it will help you but we installed an electronic wastegate actuator (not boost controller) so that we could fully open the wastegate when the restrictor was choked and we couldnt make boost to act on the wastegate spring this helps top end considerably, not to mention lowering egts and back pressure. Not sure this is even legal in group n.

Ben,
It wont be legal in GrpN but it would be nice in any turbo car. Have you got a partnumber for this? Single output PWM driven?

Thanks
Martin

[Martin]

Martin,

I do a lot with restrictor subi's, you need to close up the comp on air temp for timing, dyno run the air temp could start at 20degs and be 50 at the end of the run, so adding timing to low rpm and then on a stage it can go up and be over the limit. The ring lands breaking is very common on the cast pistons on the twin scrolls if not tuned right, also look at running .8 for 200kp and .77 above to 250 and above at .76, it will reduce lag, keep the pistons together, and peak torque at full boost will go up, VF turbo is not a happy turbo pushing big boost with leaner AFR like other turbo engines, egt's go up, pistons temps go up, ring lands break.

Run air temp comp at 0 for 20degs and then -1 deg for every 10degs AT on 120kpa and up, also look at your cams map, more power in that, also boost map would be better with a 3d map with TPS varrying boost, makes it easier to drive, less cooking the brakes left foot braking, also put 2% fuel in #2 on positive pressure.

Cheers
Michael

Hi Michael

Im surprised that it wants to run that rich. Normally if you lean in out the power will go up? The pistons used were the RA type, supposedly the better ones...please give me your comment. I understand exactly what you mean by the AT ign trim problem. At what temp do you run your 0deg trim? Please look at the attached picture of an IAT calc spreadsheet and what u think of the values. If you want i can get the specific model of the turbo for you. Are there certain ones that are better for restriced applications?

Thanks alot for the other info, ill have it put into the map and try it out. If you have by any chance a map that you are willing to share i would really like to learn from it.

Will probably take the car to a DYNAPACK 4wd hubdyno soon. Will post the graphs if anyone is interrested?

Thanks alot for your input

Martin

[Ben-S]

The corrections you post a for fuel not timing... see the link for some info on the turbo's you can get away with using in groupn

http://www.scoobytuner.com/tuning/?tSfID1=4&tuningID=43

[Martin]

Yes i know, but what are your comments?

Looks like big trims hey....or am i just too conservative

[msgofast]

N12 the only turbo you can use is a VF36, twin scroll, VF37 fits but not legal on the spec c.

email me msgofast at optusnet dot com dot au and i will send you a map with something that might help.

also are you using a std 2 port boost solinoid or prodrive 3 port? and you using a prodrive restrictor and inlet pipe?

On any other turbo engine .85 is good for the best power, but on an EJ running big boost they are better with .76 at 250kpa, easiest way to tell is to dyno to what makes the best power, not what you think you should tune to.

IT corection, 20degs =0 30degs= -1, 40= -2 and so on.

[Martin]

N12 the only turbo you can use is a VF36, twin scroll, VF37 fits but not legal on the spec c.

email me msgofast at optusnet dot com dot au and i will send you a map with something that might help.

also are you using a std 2 port boost solinoid or prodrive 3 port? and you using a prodrive restrictor and inlet pipe?

On any other turbo engine .85 is good for the best power, but on an EJ running big boost they are better with .76 at 250kpa, easiest way to tell is to dyno to what makes the best power, not what you think you should tune to.

IT corection, 20degs =0 30degs= -1, 40= -2 and so on.

Hi Michael,

We are using the standard boost control valve. The restrictor is the prodrive one, not too sure about the inlet pipe itself but it is a silicone hose type (black). The car has been built by AUTOTEK in the UK.

Ill definately try the mixtures you suggest. Ive sent you a mail, thanks for you offer.

Martin

[Martin]

Pictures of the failed parts...

This is piston1.. ( 1 is the first piston on the crankshaft from the crank pully...standing infront of the car looking at the engine, the piston closest to you on the left hand side)