My "Stroker" project

[Rusty]

Superb!

[Audi_CQ]

Roger - can you do a big write up on yours? The more info/pics the better - this is great stuff to read.

I've planned to do it, but haven't found time yet. Job, family and the car takes it all I'm afraid But some day......

Cheers,
Roger

[Audi_CQ]

How high to the Strokers rev?

What is limiting the peak revs?

I'm using soft cut at 7300 and hard cut at 7500.

Peak revs limited by hyd. lifters.

Cheers,
Roger

[Audi_CQ]

Yeah - but off boost torque is crap anyway - you can't say it is usuable power or tractible - a car with 8.0:1 is still very driveable - when you need to potter around or cruise.

Off boost torque is crap compared with what? My 2.5 is much stronger off boost then a 2.3 20v (7A) , but then I was used to a 2.2 10v so the only way was up

Cheers,
Roger

[Greg_S]

Excellent write up marco, Ive read it and had a little time to digest it and im very impressed. Roger it would certainly be good to see a good write up of your car also.

Greg

[martinjs]

Thats quite amazing marco, excellent write up.
Custom made pulley

martin

[Doug_RS2]

Off boost torque is crap compared with what? My 2.5 is much stronger off boost then a 2.3 20v (7A) , but then I was used to a 2.2 10v so the only way was up

I meant compared to on-boost levels!

The 7A is not torquey - it has a very peaky power delivery.

[S2 Ant]

Marco thats amazing!! As said further up, you're attention to detail and research is superb but then to take the time to share all this info with everyone on here is just excellent.
Makes for a very good read, as Martin said, shame you're so far away!!!

Will be good to see the car sometime and hear / watch that running!!!

Hope the rest of the planned mods go smoothly.


Yet another great car and education brought to us by this forum!!!

[newsh]

Brilliant Marco! Looking forward to reading the ongoing story.

[Erikb]

Very interesting thread! Amazing job Marco, I am impressed!

[Pisobiker]

Thanks for all the comments guys.
If this projects turns to be a success part of the merit is of S2forum's community, anyway. I have captured many tips and infos from here that turned out being crucial for the conversion, as well as having had friendly and nice help from many of you on finding and buying a lot of the parts needed.

Will try to answer all the questions you might have so far, so here some:

- Doug is absolutely right. I should have tryed to check oil getting some pressure before first startup. I anyway gave a very good lubrication to all the moving parts during engine reassembly, so I don't think I should have caused damage. Moreover oil couldn't go to the head, whose lifters and camshafts had been reassembled the day before using great amounts of oil, while being free to go through the bottom end.

- final bore was 81.5 (which actually wasn't so clear in my report). Conrods are from Pauter.

- my custom made CAMPULLEY: I'll certainly post pictures and specs of the campulley. Just a few days to have it finished.

- @ Tom: about boost level, with my actual (calculated) 8.6:1 CR I too think I'll not be able to go much higher than 1.8-1.9 bar peak boost on pump gas as well. Maybe with an efficient intercooling and a turbocharger running in the high efficiency range this could be rised to 2.0-2.1, which on the 2.5L engine should still give quite a strong torque (let me guess ~650 Nm). Keeping a good sustained boost up to the redline, with the right turbocharger and aux sistems, the 500 Hp goal shouldn't be so far.

- SACHS Racing sintered metal clutch seems to work very well. Cannot find substantial difference with OEM. Just a slightly rougher engaging behaviour while modulating the pedal in traffic lights. If the clutch really takes the +150 Nm promised I definitly give it a +

- Conrod's manufacturer claimed for my application up to 8000 rpm as much as inertial loads are concerned. I won't ever go that high, and using hydraulic lifters I'm thinking of staying with the OEM 7300 rpm redline.

- Even if it has been "stroked", this engine actually seems revving very happily in the higher ranges. It seems to me even better than the old engine. This might be due to the flywheel+pressure plate lightening, and crankshaft balancing, but everything still needs to be fully veryfied.
At the moment the only limiting factor I can see is a substantial boost reduction past the 5000 rpm, while I don't want to exceed the 6000 rpm for the moment.

- Low torque IS sensibly increased. Of course the difference isn't like having put a 5L V8 in the engine bay, but the increase, together with the turbocharger getting boost much earlier, makes the driving much more fun.
I can already tell you throttle responce even at 1800-2000 rpm is surprising.

I will post detailed comparison power and torque figures once ddone with the brake in procedure.


Marco

[auditude]

Marco,

Great job and great post! Would it be okay if I tried to copy some of what you are doing?

Will you be posting the specific dimensions for your conrods and pistons, perhaps even the job tickets or ticket numbers from the manufacturers? Also, will you be offering your custom cam pulley to those that might be interested? I heard the 16v adjustable pulleys work on the 20v's, but perhaps with less adjustability?

Once again, I think your project and that you're sharing it with the rest of us is great. Your stuff looks very well done!

I feel better about my own stroker project being able to see someone else do it successfully first. So far, the "big pieces" I have for mine are the stock 95.5mm short block, 20vt head, and custom intake and exhaust manifolds.

Keep up the excellent work, Marco!

Roger, I'd love to hear and see more about your stroker too.

Ken

[Audi_CQ]

I meant compared to on-boost levels!

The 7A is not torquey - it has a very peaky power delivery.

OK, agree but off-boost isn't bad, it's just onboost that's so insane

[Audi_CQ]

@Marco:

What cams are you planning to use?

About boost: With the right cams, a good flowing head, large turbo and IC, you don't need so much boost to get 500bhp. 1.5bar should easily do it, less if your setup is good
The downside with cams with more duration and a large turbo is that you don't get boost before 3-3500 in high gears and 4-4500 in first, but when you get boost.......

Cheers,
Roger

[Pisobiker]

Ken,

specs I gave to JE for the pistons where:

- 81.50 mm final cylinder's bore;
- compression height: same as OEM;
- wrist pin: 22mm (instead of 20mm OEM. Pauter suggested this)
- intake valve pockets 0.5 mm deeper than OEM;
- dish on top: 11cc more than OEM.

Latter spec has been misunderstood from JE. I didn't give total negative volume at first, because I didn't have precise tools for measuring the part between the two valve pockets, which is irregular and with a protruding squish area. So I inteded leaving to them figuring out what it was about, + the 0.5mm valve recess increase.
But after the problem I had I have been forced to give them a total number, which in the case was 17cc (I measured 5.1 cc negative volume for OEM pistons).

About the conrods, following is Pauter ticket.

The campulley: still havn't finished it. Too busy at work and with family. Anyway the job is pretty complex, expecially because of the need of fitting the internal pickup's timing disk.
Only if you run a ABY-AAN-ADU engine management system (one coil per cylinder) you need to fit this disk, otherwise the Audi-VW adjustable pulley such as Kentcams or Catcams sell, are good enaugh (and at a fair price).
My one takes a lot of time to be made and also needs a OEM pulley to be "cannibalized".....

You'll see what I mean when I'll post the pictures once done with it. I would have avoided doing the pulley job, but unfortunatly I'm not aware of anyone selling adjustable pulleys with the pickup disk (which in my case needs to be retimed as well).
One of my friends ordered one from Catcams mid of December (he owns a RS2). It didn't arrive jet and the italian dealer wasn't 100% sure it was compatible with the pickup....

About the camshafts:

I'm using OEM RS2 exhaust and ABY intake (the ones already fitted in my previous setup).
I will try them on different advance timings. will also try NM cams I have spare.
Biggest limit here is not having an internal adjustable cam gear for also tuning the timing of intake vs. exhaust.... Cannot afford 1000 euros for adjustable cams right now.


Marco