Where does a 92.8mm stoke 5cyl crank come from?

[mbcouple]

I think it should help the bottom end quite abit. I am going completely custom, so i wanted the extr displacement. I started with a eurovan botom, but with the added 15mm on the deck, and a stroke of 95m, it just seemed to large, so i wanted to use the stock aan block. The only way i see to go to 2.5 is the 92.8mm stroke with a 82.5-83mm bore. Anyone know if there is a 5cylinder 92.8mm stroke crank available without having a billet one made?
Thanks
Hans

[Lee]

Sounds interesting. Avoid a custom crank unless you have lots of cash to throw at your project. I hope you find one as this sounds like an interesting approach, since you get the larger displacement whilst maintaining some high rpm potential. Siena, Vagparts, other parts dudes, any ideas on a stock 92.8 crank?

[Stick Insect]

I have a 7A engine 82.5 mm bore, What rods would be needed to suit this conversion?

2.5Litre on my 20V would help the torque.

It'd be an idea to grab a crank from a scrap yard whilst they are available...

just got to wear my engine out first, another 180K to go yet.

[Vagsport]

If you're building a 2.5L for turbo applications, don't use a 92.8mm crank in conjunction with an 82.5mm bore, as due to boost pressure, an absolute seal between cylinders and gasket is essential. The bores are too big. A 92.8mm crank and 82.5mm bore will give 2,480cc, as Lee correctly worked out. The 2.5L for turbo applications is a 95.5mm crank combined with stock 81mm bores, which will give exactly 2,460cc. It is 20cc's down from your original choice, but with a longer stroke, torque is greater at low speeds, exactly what you want if using a turbo bigger than a K26 (26/27) and 7A / ADU ex. cam, where lag may be more exaggerated

On the other hand, if you want to build a N/A engine with massive torque / PS, you can use 83mm pistons, combined with the 95.5mm stroke. This will give you 2.6L (2,584cc).
HTH

Siena

[Stick Insect]

Thanks Sienna,

I like the sound of 2.6 litres

I know all about turbo's not sealing from Tuning metro turbos!
What do I need to look for in a scrapyard please? I will store the parts for future use.

Crank from ?
13mm shorter rods from ?

David

[Beppo]

Originally posted by Vagsport
If you're building a 2.5L for turbo applications, don't use a 92.8mm crank in conjunction with an 82.5mm bore, as due to boost pressure, an absolute seal between cylinders and gasket is essential. The bores are too big. A 92.8mm crank and 82.5mm bore will give 2,480cc, as Lee correctly worked out. The 2.5L for turbo applications is a 95.5mm crank combined with stock 81mm bores, which will give exactly 2,460cc. It is 20cc's down from your original choice, but with a longer stroke, torque is greater at low speeds, exactly what you want if using a turbo bigger than a K26 (26/27) and 7A / ADU ex. cam, where lag may be more exaggerated

On the other hand, if you want to build a N/A engine with massive torque / PS, you can use 83mm pistons, combined with the 95.5mm stroke. This will give you 2.6L (2,584cc).
HTH

Siena

Hi there.

In the engine im building i have 82mm bore and 95,5mm stroke. This will give my 2,5l ( 2520cc ).

Together with altered pistonhight and 144mm Verdi rods.

Pistons from Nural and crank from AudiSport.

I hope it will work nicely =)

[mbcouple]

I had heard that the 95mm stroke killed highend performance. I have seen graphs where it drops off dramaticly at 6k. I didn't know if this was a problem with their head work, or if the stroke was just too long. I have also seen a 20v running 35lbs of boost with a 83mm bore. The problem is seening and hearing too many conflicting elements. Will a eurovan(95mm stroke, 81mm bore) bottomend support a high-reving head? I want a 9500rmp motor. I allready have the eurovan block, but didn't want to waste the money on conrods and pistons, if it wouldn't work.
Thanks
Hans

[Stick Insect]

Long strokes can suffer from bore wear due to increased piston speeds, I have a long stroke Midget engine which will rev to 6500, change to a cross flow alloy head and it will manage 7500. at 9,500 RPM you need very trick stuff indeed and good oil. very good oil.

David

[Mihnea]

Originally posted by mbcouple
I had heard that the 95mm stroke killed highend performance. I have seen graphs where it drops off dramaticly at 6k. I didn't know if this was a problem with their head work, or if the stroke was just too long. I have also seen a 20v running 35lbs of boost with a 83mm bore. The problem is seening and hearing too many conflicting elements. Will a eurovan(95mm stroke, 81mm bore) bottomend support a high-reving head? I want a 9500rmp motor. I allready have the eurovan block, but didn't want to waste the money on conrods and pistons, if it wouldn't work.
Thanks
Hans

If you want a 9500 RPM motor, stick with the 2.2l block and have solid valve lifters installed, there's no way in hell the stock hydraulic lifters can take 9500 RPM more than 1 time and it will surely end up with major engine damage.

The limit on stock hydraulic lifters is around 7600 RPM, provided you don't go there all the time, otherwise 7400 is the maximum.

HTH,

Mihnea

[RSCoupe]

There was a stroked motor dynoed a year ago here in the states. It was tuned by Tom S. from T+S Tuning in Germany.

2584cc
534 HP @ 4862 rpm
784 NM @ 3995 rpm

They also did a highly modified 2226cc motor:
467 HP @ 6732 rpm
649 HP @ 4837 rpm

All numbers corrected 25% for driveline losses.

The Excel file is here:

http://autos.groups.yahoo.com/group/Audi20V_Kruemmer/files/S4dyn1.xls

You have to be a member of this group to view.

[Beppo]

Matte S

Originally posted by mbcouple
I had heard that the 95mm stroke killed highend performance. I have seen graphs where it drops off dramaticly at 6k. I didn't know if this was a problem with their head work, or if the stroke was just too long. I have also seen a 20v running 35lbs of boost with a 83mm bore. The problem is seening and hearing too many conflicting elements. Will a eurovan(95mm stroke, 81mm bore) bottomend support a high-reving head? I want a 9500rmp motor. I allready have the eurovan block, but didn't want to waste the money on conrods and pistons, if it wouldn't work.
Thanks
Hans

Here in sweden there is a S2 with 2,4 or 2,5l engine with 809hk that revs about 7000-8000.

So stroke or no stroke. There is power.

[Mihnea]

Originally posted by RSCoupe
There was a stroked motor dynoed a year ago here in the states. It was tuned by Tom S. from T+S Tuning in Germany.

2584cc
534 HP @ 4862 rpm
784 NM @ 3995 rpm

They also did a highly modified 2226cc motor:
467 HP @ 6732 rpm
649 NM @ 4837 rpm

All numbers corrected 25% for driveline losses.

The Excel file is here:

http://autos.groups.yahoo.com/group/Audi20V_Kruemmer/files/S4dyn1.xls

You have to be a member of this group to view.

Hmmm, I know those cars, I've seen the graphs and so on, and in my opinion, 25% as a driveline loss correction factor for figures measured at the hubs isn't right. The correction factor for measurements at the wheels is between 22 and 27% depending on the cars and their tire sizes, and I really don't think that one can say 25% is ok for measurements at the hubs as many people do in the US.

Just my 0.02 Euros worth of dyno tuning,


Mihnea

[mbcouple]

I already have solid lifters, i was ready to go until i heard the 95mm stroke was too long and would rob me of post 6k power. What the point of a turbo if you can't run it up.
Hans

[Mihnea]

Originally posted by mbcouple
I already have solid lifters, i was ready to go until i heard the 95mm stroke was too long and would rob me of post 6k power. What the point of a turbo if you can't run it up.
Hans

Running up in the rev range is meant for VTec engines, dude

The point is that you need huge cams in order to get air inside the engine at high RPMs and anyway, 9500 RPM doesn't sound right to me, I'd say 8500 would be enough for a street engine, especially for a street engine in the US....


For what it's worth, the Audi 90 IMSA engine used to put out 730 HP from 7500 to 8500 with a redline at 8700 RPM, and that was with a 2.1 liter engine running 3.3 Bar absolute boost from 4500 RPM up to the redline...

The turbo on that beast was a K27 #16 hot side with a 34 compressor wheel.

HTH,

Mihnea

[mbcouple]

I want it to run up to 9500. I don't want to run it that far. I would like to over build the car, not only for bench racing statistics, but to have it when you need it. I will probably seldom take it over 8k, i just want it there so i will never have regrets with the car. I am building the motor from the ground up. Every piece is off, and has been hot tanked or replaced. I am not a "ricer," but deeply vested into german cars. I have a 928s4, a real 32v amg from their early days in 1985 before the buy out, and several other plain jane cars, 300e, 380sec, 500sel lorinser. I want this to be the best motor i can build within my means and mechanical know-how. This is my firs 5 banger, and my first audi. I just want it to out perform the easy route of a supercharged 928. Right now for a $3500 investment you can boost the 928 into the 550-600hp range with no internal mods.
Hans