Thinking about an under drive crank pulley for my 305, good idea?

[cubandeathgrip]

Is it worth it? And if so where can I find 305 paraphernalia for my truck motor?



thanks

 

[1998_K1500_Sub]

Is it worth it?

I've got an underdrive kit I'm willing to sell you...

Does that tell you something?

Obviously it slows the cooling fan and AC compressor, and since you're a Florida guy (yes?) that might be a concern. Or not.

- AC compressor compresses refrigerant; volume of refrigerant compressed is a function of compressor RPM

- AC condenser facilitates exchange of heat from refrigerant to air

- Cooling fan draws air through condenser to rid refrigerant of heat; mass of air drawn, and thus amount of heat removed, is function of fan RPM

- Cooled and now liquid refrigerant evaporates and makes driver comfy

 

[RichLo]

Been there done that in other vehicles. While 100 pennies add up to a dollar, are 2 pennies worth 50 bucks? E-fans give much better results for the price if you haven't done that yet. Once you do better bang-for-your-buck stuff first then yea, go for the pulley. It'll give you a few mindpower HPs.

The 305 is what it is, you can polish it but you'll always be 45ci behind a 350.

 

[L31MaxExpress]

Never noticed a loss of a/c performance in either my Express van or my Tahoe. In fact if anything it cooled better going down the road with less compressor cycling. I had my idle speed on both raised to 750 in drive and 800 in park. I had better results keeping the clutch fan than with electric fans.

 

[1998_K1500_Sub]

Never noticed a loss of a/c performance in either my Express van or my Tahoe. In fact if anything it cooled better going down the road with less compressor cycling.

Interesting observation and explanation. No argument from me.

By my estimate the problem would be at low speed / low RPM, urban / suburban driving, including stoplights.

 

[L31MaxExpress]

Interesting observation and explanation. No argument from me.

By my estimate the bigger problem would be at low RPM / speed urban driving, and stop and go.

My idle speed on both was raised for the cams in them. Compressor and fan were actually spinning faster than at stock idle even with 25% underdrive on the compressor and 33% on the water pump and fan. A/C cooling has never been an issue even in traffic.

 

[1998_K1500_Sub]

My idle speed on both was raised for the cams in them. Compressor and fan were actually spinning faster than at stock idle even with 25% underdrive on the compressor and 33% on the water pump and fan. A/C cooling has never been an issue even in traffic.

On my Suburban I actually use a smaller pulley on the AC compressor than stock size (112mm vs. 130mm).

As a consequence, I had to "tune" the compressor cut-out parameter in the ECU to 3000RPM so as to not overspeed the compressor, but I almost never run the engine that fast for any length of time so... that's my trade-off.

 

[L31MaxExpress]

On my Suburban I actually use a smaller pulley on the AC compressor than stock size (112mm vs. 130mm).

As a consequence, I had to "tune" the compressor cut-out parameter in the ECU to 3000RPM so as to not overspeed the compressor, but I almost never run the engine that fast for any length of time so... that's my trade-off.

I have a Sanden SD7 based compressor. Good to 6K in short bursts.

 

[1998_K1500_Sub]

I have a Sanden SD7 based compressor. Good to 6K in short bursts.

Yeah, me too. Looks like they're good for 6000RPM at the compressor constantly, higher for short time. Given my regular crank pulley and the smaller compressor pulley, I figured the 3000-engine-RPM compressor cut-out would prevent any mishaps with the compressor.

 

[cubandeathgrip]

I've got an underdrive kit I'm willing to sell you...

Does that tell you something?

Obviously it slows the cooling fan and AC compressor, and since you're a Florida guy (yes?) that might be a concern. Or not.

- AC compressor compresses refrigerant; volume of refrigerant compressed is a function of compressor RPM

- AC condenser facilitates exchange of heat from refrigerant to air

- Cooling fan draws air through condenser to rid refrigerant of heat; mass of air drawn, and thus amount of heat removed, is function of fan RPM

- Cooled and now liquid refrigerant evaporates and makes driver comfy

Thanks for the feedback, am looking to get a better MPG and willing to do this experiment to see where it may lead. If you are seroiuses about selling me an underdrive kit , I am interested in buying that from you. Thanks