Fuel's Winter Project: Build It Before It Blows

Whoa..That's a big turbo! Lol

How the hell you gonna get a turbo Blanket on that HOG

Im Jelly

Okay so I bought an ATI used from Steve Poe late last fall for my new engine. It was advertised to be the stock size so I didn't even bother to check it and stuck it in the parts pile. Well today I am putting all my accessories on the engine, then put the belt on. Well the tensioner bottoms out with the belt on and the belt is not tight. Throw a tape measure accrosed the ati and then the stock damper. This ATI is not the same size. It looks to be 5.5" where the stocker is 6.5". My question is this will under drive everything correct? Will this hurt anything? I dont want to buy new pulleys.


So can anyone help me with belt length please? I am a turbo guy so I don't know about this belt stuff lol

Use a tape measure to get belt length. Just run the tape measure the same way the belt will be routed for length. It should run everything fine but it will spin everything faster if it is a smaller diamater. It is another way to spin your S/C faster for more boost.

ZmanM3 said:

Use a tape measure to get belt length. Just run the tape measure the same way the belt will be routed for length. It should run everything fine but it will spin everything faster if it is a smaller diamater. It is another way to spin your S/C faster for more boost.

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Actually the smaller crank pulley/dampener will spin all the accessories slower, not faster. It's the pulley on the actual accessory that if smaller will spin faster but the just like on a bicycle, the bigger gear by the pedals makes the bike go faster and the smaller one on the rear tire will make the bike go faster.

As for the OP, a full inch smaller really seems quite small so I would suspect your accessories will be severely under-driven. I just looked at a pulley rpm spreadsheet and changed the crank pulley to 5.5" and for a comparison, stock size at 6500 rpms the alternator would spin 18,133rpms and with the underdrive 15,343. at 750rpms crank speed the alternator would be 2092 rpms vs 1770.

I wouldn't use that dampener. A 10% underdrive should be 5.875" so that's more than 10% smaller.

I did get that backwards, thanks for correcting me.

I am not sure if it is a full inch. That was just a quick measurement with a tape measure. I will try to get a little more exact reading.

I just looked on ATI's website. The only undersize that they sell for this engine is a 5.5" which is a 15% under drive. Being my car will still be a still car what should I do? I do plan to spin the engine pretty hard, but don't want to suffer from not enough water circulation or alt volts when cruising.

Check out ATI'S blem store on ebay... I got mine brand new for 250 I think. With how goofy these cars act with low voltage situations I wouldn't put that on there

I just spoke with Mo about it and he said I won't notice anything. He said not to worry about it. I guess I will find the right belt and run it.

JoshK said:

I just looked on ATI's website. The only undersize that they sell for this engine is a 5.5" which is a 15% under drive. Being my car will still be a still car what should I do? I do plan to spin the engine pretty hard, but don't want to suffer from not enough water circulation or alt volts when cruising.

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The ratio of any two drive accessories can be determined by dividing the diameter of the smaller pulley into the larger one. For example, if a 6-inch water-pump pulley is used in conjunction with a 7-inch crank pulley, the pulley ratio is 1.16:1. So for every 1,000 rpm the crank pulley spins, the water pump would rotate 1,116 times. Since the water pump spins at a faster rate than the crank, it's said to be overdriven. Flop things around, and the water pump would spin slower than the crank and be underdriven. Underdrive pulley sets are often used to reduce the parasitic drag on the crankshaft to increase horsepower; however, altering the speed of the accessories can have adverse affects on the performance of the related systems, especially if they are already overburdened.

I know you dont want to buy pulleys
But to run that UD Crank pulley Damper, You should reevaluate the systems performance based on the formula above
I would run the math on the stock pulley and damper and then run it on the 5.5 Damper do the math and see what pulleys need to be changed on the accessories

Does anyone know the ratio or rate that under drive sets slow things down?

OEM crank is 6.78
My ATI is 5.5
This is from ATI website

Edit: just found that steeda claims to slow down the accessories by 25%. Will the difference in crank pulley sizes equate to the same 25%? ATI says the damper I have is a 15% under drive so it should be less than running actual under drive pullies correct?

A couple updated pics of the progress. I have been working on the up pipe. Had some stuff on order for over a month that held up the down pipe fab, but that is supposed to finally come in tomorrow hopefully.

A couple updated pics again for you guys.

Progress!

For a moment I thought it was Billy's but seeing he will work with it again I see it isn't. Looks great!

Yes sir Manuel, you have another car with a JPC Billet intake to tune now.

Nice intake!

Looking good
Did you get the pulleys figured out