VEMS Engine management systems, plug & play ECU upgrade

[Eldavo]

Probably Wossners.

 

[blade7]

Most likely what I'd use if I was rebuilding a 2.5. Probably stating the obvious, but they run a fair bit more clearance than the original pistons. Around .003-4" I think. If you're feeling flush have some windage ports machined into the block too.

 

[Eldavo]

Most likely what I'd use if I was rebuilding a 2.5. Probably stating the obvious, but they run a fair bit more clearance than the original pistons. Around .003-4" I think. If you're feeling flush have some windage ports machined into the block too.

They need more clearance or have more clearance?

Windage ports - talk to me???

 

[blade7]

Most likely what I'd use if I was rebuilding a 2.5. Probably stating the obvious, but they run a fair bit more clearance than the original pistons. Around .003-4" I think. If you're feeling flush have some windage ports machined into the block too.

They need more clearance or have more clearance?

Windage ports - talk to me???

AFAIK forged piston like the Wossners expand more than cast pistons, therefor require more cold clearance. The original pistons have an expansion rate very similar to the block and run very tight clearances. There's been a few tears when people have tried to run factory clearances with aftermarket pistons. I expect Wossner supply info on clearances. The windage ports are something the 2.7 and 3.0 blocks had from the factory. Have a look on Lindseys site for pictures and info about machining them into 2.5 blocks

 

[JC]

Would I use Wossner pistons in an Alusil bore again?
https://rennlist.com/forums/924-931-944-951-968-forum/1099319-wtb-944s2-engine-or-block.html
What do you think!!!

Probably Wossners.

 

[924Srr27l]

Would I use Wossner pistons in an Alusil bore again?
https://rennlist.com/forums/924-931-944-951-968-forum/1099319-wtb-944s2-engine-or-block.html
What do you think!!!

Probably Wossners.

I couldn't see anything in the posts which said the Pistons were Wossners and at fault? Engine Failures are reliant on so many
things that the Builder does, what he specs and how they are fitted etc...

Lindsey Racing sourced my 3.0 block, honed it to 105mm and measured & ordered bespoke Wossner Pistons for a short stroke 2.7 Capacity and 10:9:1 CR
They came with a coating on the skirt, and look different to the pics in the rennlist postings

The Engine was build by one of the best in the UK with decades of building 944 Race Engines, I ran it in exactly as Lindsey Racing told me which was to never stay at any one RPM, but to "Load" the engine and in their own words "Not Pussy around", this I've done many times with Nicasil 2 stroke Engines (Ran them in Hard) after getting them warm, and also Lindsey Said run the car for long runs (2+ hours at a time)

The Engine was used 4500rpm for 500 miles then was dyno'd and taken to the rev limiter at 6200rpm.

So far so good, the Wossner's have been faultess in 6000 Road miles but also 4 trackdays, and 2 (2 hour) Races...

http://924srr27l.co.uk/wp...s-1000307-1024x681.jpg

http://924srr27l.co.uk/wp-content/uploads/2015/05/wheels-1000323-1024x681.jpg

http://924srr27l.co.uk/wp.../IMG_5115-1024x768.jpg

R

 

[JC]

I know they are Wossner because that was my engine,

 

[blade7]

I know they are Wossner because that was my engine,

I read a similar tale about the Mahle Motorsport pistons that are available now, you'd assume Mahle know as much as anyone about Alusil compatible piston coatings. Jet951 on the forums has used the Wossner pistons for years in his S2 turbo engine. If I ever rebuild an Alusil block I'll definitely measure the bores after the machining and polishing. No doubt there are others, but the only 2 shops I know of in the UK that have a good reputation with Alusil are Capricorn and Serdi.

 

[PSH]

Hi JC

Sorry to hear/see this is your engine, I read through the rennlist thread but couldn't see if there had been a final solution/reason to why this happened, could you enlighten us, please?

Cheers

Pete

 

[924Srr27l]

The damaged Pistons have several small Anti detonation / Contact Reduction grooves at the top, I've seen Carillo, Wiseco, & JE make these but I can't see any (online) made by Wossner?

R

 

[JC]

Hi JC

Sorry to hear/see this is your engine, I read through the rennlist thread but couldn't see if there had been a final solution/reason to why this happened, could you enlighten us, please?

Cheers

Pete

I asked for opinions from around 6 expert engine builder (Porsche transaxle) responses were,


1/ "I've had 2 engines self destruct this year, I've had it with Wossner, I'm using Mahle motorsport now"
2/ "Definitely compatibility issue"
3/ "I have heard of problems with Wossner in Alusil bores"
4/ "looks like the skirt coating has failed"
5/ "are you sure the machinist prepared the block properly" (answered in Rennlist thread)
6/ "coating failure"
Even the supplier said that it looked like the coating failed, he tried to get me some compensation to rebuild the motor,
Wossner gave me a full refund but refused to accept blame, they said the ring gaps were too small, I know this was not the case.
I've moved on and in fact the supplier sold me a set of Wossner 104mm at cost price ( these are being used with Iron liners)

 

[JC]

The damaged Pistons have several small Anti detonation / Contact Reduction grooves at the top, I've seen Carillo, Wiseco, & JE make these but I can't see any (online) made by Wossner?

R

This seems to have them, https://www.vividracing.com/wossner-22l-88mm-121-pistons-honda-prelude-h22-9296-p-132214.html
on a different note, your coating looks darker to me and also covers the underside of the skirt

 

[PSH]

Thanks, for the detailed response JC, I have read of a few failures using Wossner pistons, the main reason why I avoided them when rebuilding my own engine. I note you state you're going to use iron liners, is this with Wossner pistons? I think that you may need to take a closer look at ring gaps when using Iron, I believe the gap required may be different to Alusil which i guess is partly due to compatibilty, or so I read.
I guess all those answers can be right in one measure or another, personally, I would go with ring gap too small, I would ask what power output the engine was expected to give but going by what you're said doubt it ever got to WOT, more power needs bigger gaps. There is a formula which I've forgotten, I used it to calculate my gaps and then spoke to the piston manufactures technical department to see if they agreed with my maths, which luckily they did, or I'd have been scratching my head not knowing where I was
I did read your Rennlist thread and was surprised seeing cross-hatching on the bores, from what I understand there shouldn't be any, there certainly wasn't any on mine.
From what I recall the advice given by LR for running in is spot on, your use of mineral oil to bed the rings in is also spot on. I didn't use the additive that you did but can only see that as a good thing for your engine, not bad.
I can only imagine your disheartening after the engine first failed, twice is unbelievable, I truly hope it's third time lucky and your cars gives you many more years of free of incident running.

Regards

Pete

 

[JC]

Thanks, for the detailed response JC, I have read of a few failures using Wossner pistons, the main reason why I avoided them when rebuilding my own engine. I note you state you're going to use iron liners, is this with Wossner pistons? I think that you may need to take a closer look at ring gaps when using Iron, I believe the gap required may be different to Alusil which i guess is partly due to compatibilty, or so I read.
I guess all those answers can be right in one measure or another, personally, I would go with ring gap too small, I would ask what power output the engine was expected to give but going by what you're said doubt it ever got to WOT, more power needs bigger gaps. There is a formula which I've forgotten, I used it to calculate my gaps and then spoke to the piston manufactures technical department to see if they agreed with my maths, which luckily they did, or I'd have been scratching my head not knowing where I was
I did read your Rennlist thread and was surprised seeing cross-hatching on the bores, from what I understand there shouldn't be any, there certainly wasn't any on mine.
From what I recall the advice given by LR for running in is spot on, your use of mineral oil to bed the rings in is also spot on. I didn't use the additive that you did but can only see that as a good thing for your engine, not bad.
I can only imagine your disheartening after the engine first failed, twice is unbelievable, I truly hope it's third time lucky and your cars gives you many more years of free of incident running.

Regards

Pete

Thanks Pete,
The cross hatching was not visible when it was freshly machined, it only visable upon teardown, the machining procedure outlined in the responce from the machinest does mention a cross hatch

Re. the ring gaps, the latest info from the supplier is

"The very latest I have on Ring gaps from NPR via Wossner is as follows:

1st ring: 0,25 – 0,40 mm
2nd ring: 0,35 – 0,50 mm
OCR: 0,20 – 0,70 mm

these dimensions are okay for Ø 101,60 – 106,00 mm.


I got this info on Oct 17th this year from Kevin, one of the lead engineers at Wossner.

Make sure that the 2 compression rings are installed with the label, which is at the end of the ring, is installed facing up.

Thanks"

I have emailed them to confirm correct gaps for Iron liners

 

[blade7]

I wonder if the damage would have extended that far down the bore if it was an issue with the ring gaps.

 

[PSH]

Yes, IIRC the compression rings on my pistons are shaped (a small undercut) and need to go the right way up, your 1st/2nd ring gaps are smaller than mine but mine are larger to withstand the extra heat at full bore and of course a different make piston. Number 1 ring is the most important as it gets the most heat, mine are 1st 0.45, 2nd 0.57, oil 0.77, the last two were adjusted a little from what was planned as when fitting some of them already had larger gaps, so I opened up the others to match.

The engine has done well over 20k miles now and she's a beast, rev limit is 7k+ and boost is limited by the ECU at 1.5bar although I noted recently that the stepped gauge is showing 1.55Bar, I do get carried away sometimes...

Good move checking re the Iron liners..

Pete

 

[PSH]

I wonder if the damage would have extended that far down the bore if it was an issue with the ring gaps.

I think it's due to the rings digging in and tearing up the bore which then gets pushed further down the skirt, once damage happens causing debris it can only spread

 

[blade7]

I wonder if the damage would have extended that far down the bore if it was an issue with the ring gaps.

I think it's due to the rings digging in and tearing up the bore which then gets pushed further down the skirt, once damage happens causing debris it can only spread

A pass with a honing tool may clean it off and determine if that was piston material. I'd definitely go top size on the ring and piston clearance with the shallower water jacket on the 104mm block. It could be wrong rings, clearance, a coating failure, cylinder prep, over heating or a combination of those.

 

[924Srr27l]

The damaged Pistons have several small Anti detonation / Contact Reduction grooves at the top, I've seen Carillo, Wiseco, & JE make these but I can't see any (online) made by Wossner?
R

This seems to have them, https://www.vividracing.com/wossner-22l-88mm-121-pistons-honda-prelude-h22-9296-p-132214.html
on a different note, your coating looks darker to me and also covers the underside of the skirt

Those look to have fine lines not deeper grooves like your photos, all I know is Lindsey Racing specced the Wossner's, from memory
they were $1000 a set back in 2015

https://www.lindseyracing.com/LR/Parts/WOSSNER.html

R

 

[924Srr27l]

From what I recall the advice given by LR for running in is spot on, your use of mineral oil to bed the rings in is also spot on. I didn't use the additive that you did but can only see that as a good thing for your engine, not bad.
I can only imagine your disheartening after the engine first failed, twice is unbelievable, I truly hope it's third time lucky and your cars gives you many more years of free of incident running.
Regards
Pete

Yeah I forgot to add the Oil procedure was:

150 miles - Running In Oil, (Millers CRO 10W40 Competition)
500 miles - Motul Classic (After 1950's) Mineral 20W50 low detergent
Change the Oil 6 times every 500 miles, only then after 3000 miles use a SEMI-Synthetic
3000+ Miles - Joe Gibbs Racing XP5 20W50 Semi Synth

R