underdrive pullye with turbo

[shavers55]

Alright this is a REALLY dumb question more asking for clarification..but i plan on running turbo on my 420A with stock internals..would i be able to use an under drive pulley while doing that? Also does the under drive pulley take place of the tensioner pulley? or are those two separate pulleys?

 

[96ETT]

Yes very dumb question. The turbo does not care about your pulleys. It is driven by exhaust. The underdrive pulley is just going to slow down the accessories because you typically replace the crank pulley with a smaller one. This slows down the rest of the pulleys which draws less power. But also causes everything to not be the same, less coolant flow, lower alternator current produced, weaker ac.

 

[Mischif]

Underdive pulley and tensionr pulley are two different things.

 

[curt-s]

Now that the questions have been answered, is there any particular reason why you wish to run an underdrive pulley?

 

[chadillac2820]

Less drag on the engine.

 

[DSM1G90]

Less drag, but an underdrive pulley has no harmonic balancing properties to save your crank.

Your crank develops harmonic vibrations which has to be cancelled out by the balancer, or your crank will self destruct (literally shatters) after awhile.

 

[jrohner]

But his engine will rev slightly quicker right before the crank breaks!

 

[bryanwheat]

Less drag, but an underdrive pulley has no harmonic balancing properties to save your crank.

Your crank develops harmonic vibrations which has to be cancelled out by the balancer, or your crank will self destruct (literally shatters) after awhile.

You don't have to run a different crank pulley to utilize the under drive pullies. You just use bigger pullies on the alternator and power steering pump to slow them down a bit. I don't really see the point on a boosted engine though.

 

[DSM1G90]

What I don't understand either on the OP's - underdrive pulley on a turbo setup.

Now, I know there is a upgrade kit to replace the stock hydraulic belt tensioner with a more simpler spring tensioner in which have been an excellent upgrade for some 420A users.

 

[shavers55]

so in other words dont worry about the under drive pulley

 

[keltalon]

Less drag, but an underdrive pulley has no harmonic balancing properties to save your crank.

Your crank develops harmonic vibrations which has to be cancelled out by the balancer, or your crank will self destruct (literally shatters) after awhile.

This is exactly true. Not only does the crank takes a hit but the transmission gears also suffers. Underdrive pulley absorb zero torsinal vibration on firing stroke this is not good. Here is a good read About Fluidampr

 

[DSM1G90]

To add ... why roller chain driven camshafts don't have the flex as do fibre belt driven camshafts .. due to the same power spike coming from the crank.

These have to rely on nylon runners riding against the chain to absorb the spike taken by the initial hit from the crankshaft. Belts can absorb more spikes by itself and through the tensioner pulley setups.

Only chain driven motors that uses the 'silent-multilink' chain that closely replicated the timing belt, are the choice to have intead of the roller chain drive type even though they still use nylon runners for chain tensioning. The Mitsu 4B11(T) motors uses the silent multilink chain.

GM with their 2.2L 4cyl motors have this one flaw: Block is bulletproof, but uses a single row, roller chain for the DOHC setup, and chain breakage is quite frequent with these motors. If GM used a double row, roller chain setup, then that's a winner of a motor in itself.

 

[shavers55]

so once again dont use the under drive pulley then?

 

[keltalon]

so once again dont use the under drive pulley then?

Noooo!! Lol I like to see your car run for a while especially if you beat on it .