Turbo Engine, Tranaxle, and other questions...

[Piledriver]

The stock T1 crank is fine at 4500.
Its fine at 7500 with good rods.
Running in the RPM range in between ~5200 and ~6000 will kill the block quickly.
Even if it is perfectly balanced pulley to pressure plate.

At ~5200-6000 there is an inherent vibration/ harmonic crank flex that beats the hell out of the engine case center main.

A counterweighted crank fixes the harmonic, but the design is inherently balanced---it doesn't need "balancing" counterweights ---it just needs more mass in the right places to get rid of the harmonics.
(That's why full circle counterweights can actually work on VWs. Sorta)


VW also fixed it on the T1-design based WBX motors in the Vanagons by adding mass to the crank webs.

[kangaboy]

I have a stock crank and rods without balancing and rev mine to 5200 rpm quite often. I am bumping up the rev limiter to 5600 today.
The Swedes and Norwegians are revving stock cranked 1641 engines to 7000 plus rpm and getting almost 400 hp... I think we can go up a ways from 4750 rpm.

Well this makes me happy. I hate shifting so low when I feel like there is so much more left in the motor. I'm sure a few hundred rpm will make some difference, but I'm still looking forward to the day I can get "safely" up to ~6500-7000rpm repeatedly.

So Pile, what method can be used to combat the harmonics that are generated at the ~6200rpm range? In a type 1 that is. Counterweighted crank? Equalizer pulley? Lightened flywheel?

[Piledriver]

Heavier crank, either counterweights or WBX. (major effort for latter in a t1 case, and the flywheel choices get weird, better but T4, not T1, 5 x 12mm grade 12.8 bolts instead of 8 dowels, your call)
You used to be able to get a stock stroke welded counterweighted cranks for next to nothing.
Considering what T1 cases go for these days its a good investment and cheap insurance.
I am dubious of the chinese cranks, use reputable vendor and pay to have it checked out before shipping if you go there.

For the crank, I'm talking DPR or DMS, not Bernie Bergman or a swap meet mystery metal.

I'd probably add crmo rods with good bolts, even the SCAT I-beams are probably fine for intermittent 7500 RPM use, and better for boost as they are beefier than the cheap Hbeams. Get the ARP2000 bolts if you plan to go there.

[Chip Birks]

I have a built type 1 trans in my car, based on a new aluminum Rhino case. Weddle 1-4, with a 3.88 r&p, also a spool and SAW axles. I don't have lots and lots of drag racing launches on it, but I do have a dozen or two. I have launched at anywhere from 5000-6500rpm. My car weighs 2000lbs with me in it. It has dyno'd at up to 278whp back when it had its "mild" cam and "small" turbo. I have a very heavy clutch and pressure plate, but the clutch does engage smoothly.

One big key to keeping a transmission together, is making sure that there will be no wheel hop. My car launches smooth every pass. Driving style is also critical. You have to learn how to preload the drivetrain before you launch. Shock loads break parts.

[petew]

Serious Qu; ought we be talking about 7500rpm when our OP is really just trying to get into the turbo game? Most of the turbo VWs I've seen are stopping around 6500rpm and making a LOT Of power below that too.

[Clonebug]

You can shift at any rpm you want but depending on the size of the turbo you might get into lag when shifting.
If you get full boost before 3500-3800 rpm you can shift at 5000-5200 rpm I found.
A small turbo is more flexible at shifting.
A large turbo...... Not so much.

Last but not least........rpm is hp.

The difference between reving to 5000 and 5800 is quite noticeable in hp gain In the calculators I have used.

[Chip Birks]

Serious Qu; ought we be talking about 7500rpm when our OP is really just trying to get into the turbo game? Most of the turbo VWs I've seen are stopping around 6500rpm and making a LOT Of power below that too.

I would like to get something that would scare the living piss out of me when I stomp the pedal to the metal.

I REALLY like 7500rpm in my turbo car. Nothing like releasing the 2 step and rolling out of the water box at 7500rpm with both rear tires billowing smoke. Don't knock it till you try it

I have definitely seen the car get wild well below that rpm on the street. 5000rpm and 25psi would fry the tires in 3rd at about 70mph when rolling into the throttle. After changing lanes without intending to I turned it down. Sure was fun though.

[Chip Birks]

You can shift at any rpm you want but depending on the size of the turbo you might get into lag when shifting.
If you get full boost before 3500-3800 rpm you can shift at 5000-5200 rpm I found.
A small turbo is more flexible at shifting.
A large turbo...... Not so much.

Last but not least........rpm is hp.

The difference between reving to 5000 and 5800 is quite noticeable in hp gain In the calculators I have used.

It's not uncommon for power to drop off significantly in the upper rpm areas on an actual dyno. But dropping from 250hp to 200hp from 5500-7000 still leaves you with 200hp to play with.

[petew]

I REALLY like 7500rpm in my turbo car. Nothing like releasing the 2 step and rolling out of the water box at 7500rpm with both rear tires billowing smoke. Don't knock it till you try it

I have definitely seen the car get wild well below that rpm on the street. 5000rpm and 25psi would fry the tires in 3rd at about 70mph when rolling into the throttle. After changing lanes without intending to I turned it down. Sure was fun though.

So it's really all about you Chip.

[Chip Birks]

I sure didn't build it for my wife to drive!

[Clonebug]

hp and boost especially is addicting and there is no such thing as turning it down or settling for 200 hp instead of 250 hp.......

[kangaboy]

I think you guys scared OP away...

[Piledriver]

Serious Qu; ought we be talking about 7500rpm when our OP is really just trying to get into the turbo game? Most of the turbo VWs I've seen are stopping around 6500rpm and making a LOT Of power below that too.

Even at 6500 you will rapidly destroy your case with a stock crank, even hitting it occasionally.
Room to add HP and decent reliability is a must, some headroom is a good thing.
A T1 bottom end needs all the help it can get, esp boosted.

[petew]

So what you're saying is, "get it balanced".

[madmike]

I try to bulletproof the bottom end
welded CW cranks are a must in all my motors, then checked for balance ,flywheel&pressure plate too I balance my own pistons & rods Deep sump also!