Found some toothed pulleys at the right ratio to run at 2:1 crank speed but I'm concerned that the SC pulley is a bit small (40mm) and will jump or strip the teeth off the belt when closing throttle at red line, back pressure/inertia will be quite a lot.
Is this a potential problem?? Any ideas would be great before i go ahead and start welding the charger mounts..

Try the basics and calculating ratios etc against the pressure map manufactured by eaton.

I would personally run a larger pulley than that. Depends more on the belt manufacturers recommendations. Belts have a minimum bend radius for various loads and speeds.

I would try and increase the sizes of all the pulleys by at least 50% looking at your set up.

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Originally posted by MakeEverything
Try the basics and calculating ratios etc against the pressure map manufactured by eaton.

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I think the pulleys are to small if that's an m62, if it's an m45 it's a bit on the small side for a modified 2.0L with high rev's.

I've also been looking at putting an eaton m62 onto my atmo cosworth, and after playing with the calculator on eaton's web site decided that a 1.7 pulley ratio would be best to stay within the rev range of the charger and lower charge temps.

It also depends if your changing the spec of the engine any or how much (cams/compression) as well???. If it's staying roughly as it is (guessing on spec's of course), high comp and nasp cams then you'll only be safe putting low boost in (i was aiming for 4 - 7 psi max), or drop the comp and fit milder/turbo cams and run 1.9 or 2 pulley ratio for more boost.

The only flaw in my plan was buying a merc supercharger, to find it was actualy an m45 so sold it again.

Ian

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Originally posted by flak monkey
I would personally run a larger pulley than that. Depends more on the belt manufacturers recommendations. Belts have a minimum bend radius for various loads and speeds.

I would try and increase the sizes of all the pulleys by at least 50% looking at your set up.

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Hi Ian, yes its an m45, the slk had both m62 and m45 depending on year..

its a very monkey see monkey do project TBH and not entirely sure if it will work.. I was just gonna run 2:1 on the pulleys and see what boost it made and then worry bout fine adjusting the pulley sizing after as not sure how its worked out on paper..

CR is 10.5:1 so thought a 6 psi boost might work with the intercooler I have..

The NA cams are high lift Newman phase 2, 288 dur and thought that dialing a bit of overlap out might give a decent result but had considered putting the standard turbo spec exhaust cam back in??

Any pointers much appreciated.

[Edited on 15/10/11 by Craigorypeck]

When i did some research (lots of googling) on the m45, it looked a bit marginal on a tuned 2L engine and is likely to run out of puff at higher rpm.

The 2.1 ratio will probably be needed to get some boost high up, but you'll have to balance the rev limit on the engine to what the supercharger can safely spin at.

Your comp and cams are relatively mild for a na cosworth, as you say dial out some overlap, knock some timing out on boost and use good fuel you should be ok up to 8psi. By everything i looked up/worked out, the m45 won't make that though on a modified 2L engine (if it's already making 200bhp ish) unless you spin it over it's recomended max rpm.

I read somewhere that the m45 physically can't pump enough air to make over 245bhp ish. Don't quote me on that....it's only what i read somewhere!.

Of course if your engines making say 180 ish now, then an extra 60 ponies is worth having!, plus the massive extra low down torque you get with a supercharger!.

Ian

[Edited on 15/10/11 by Oddified]

Cheers Ian.

currently estimated to be in the 180-190bhp range but all the power is up high, looking for more torque really.. a few extra up top would be cool but not after mad figures. I'd be very happy with 245 hehe..

Contacted the company i got the pulleys from this morning and they suggested that they would make me wider pulleys to run a wider belt if I run into slippage problems, which is nice..

also running 2.5" od piping all round will this suffice? also my plenum is a pretty poor shape... a lot of corners and squareness, what ill effects will this have..

I don't think it's so much the width of the pulleys that's been suggested above, it's the diameter and the tight radius the belt is going around that might reduce the belts life.

For the power your looking at 2.5" would be large enough i'd expect, avoid tight/square bends though if possible.

I'm no expert though, just passing on info that i'd found out whilst looking into taking the same path.

Ian

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Originally posted by Oddified
I don't think it's so much the width of the pulleys that's been suggested above, it's the diameter and the tight radius the belt is going around that might reduce the belts life.

For the power your looking at 2.5" would be large enough i'd expect, avoid tight/square bends though if possible.

I'm no expert though, just passing on info that i'd found out whilst looking into taking the same path.

Ian

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