To me, a small pulley is in th 2.5-2.7 range and I agree, 60's are needed. For a daily driver that rarely see's anything over 4000 rpm, you SHOULD, and i mean SHOULD, be able to run 42's on a ring as low as 2.8 and not have any issues. Obviously if you beat on it all the time, it will break regardless of what combo you are running with. 2 of the 3 of my "idiot" friends were running 60's, both dyno tuned and data logged for a few weeks.

What size pulley?

 

Is it possible to use 42lbers and a 2.8inch pulley? Yes.
Is it smart? No.
Should anyone recommend it? No.
How about on a daily driver? No!

It's just stupid to run your injectors static. Even on a daily driver, it's still stupid. Why would you want to do it? Why, its illogical to want to push you injectors to the breaking point.

Granted if you NEVER push you motor to higher rpm's it doesnt matter if you use 42lbers with a 2.5inch pulley. But if you are going to see higher rpm's you should do so knowing that your car can handle it.

Your friends must have either again had a bad tuner, or didn't have cooling mods. Cobalts that are tuned properly and have cooling mods will last. You call your friends the idiot, but yet you are doing the same thing to your car?

Why do you think your friends cars broke?

 

Where's the log, pulley size, rpm band, and TPS reading.....

 

I will post it up when I find it. How about answering my question, why do you think your friends cars all broke?

 

Back peddling is all I am seeing here....


Both were running CXR heat exchangers and meth, their issue is in bold above.

 

Out of curiosity how did they "beat" on there cars. Constantly track them, autocross them, doing donuts, racing in reverse? What do you define as beating?

 

Street racing on the weekends was the sole purpose of the two that blew up. Spend the week in the garage, come out on the weekend and hammered all weekend.

All the way to redline in most cases...

 

Sucks for them. I know of a lot of cobalts that take massive amounts of abuse though and handle it quite well. If you build your car correctly and tune it right, take care and maintain it, it will last. Cars can handle the occasional abuse if built correctly. I consider occasional as once or twice a week, such as a "weekend warrior".

Redline is defined by the tuner so that doesn't tell us much. If they were taking it over 7500 rpm's often without a built valve train that would explain a lot.

 

They were both set at 7200, Of the people with 60's and 2.6, one had piston issues, the other is believed to have been a head gasket.

I searched on HPT forums and found this nifty little line... Take it for what it is worth.

SO, back to my original statement, you can run 42's if you want to. I will revise my earlier statement to running them with the ring that you and your tuner are comfortable with.

I would still like to see the IDC logs when you get them up....

 

gm stage 2 untouched on the 3.06" ring.

Also try to remeber the rpm is not as important as the pressure each new ring is bringing, with that pressure comes the heat.

 

is that saying 115% IDC with a 3.06 pulley????

 

Yes, the gm tune is rather rich

 

thats well over its duty cycle, wouldnt that be lean? i dont know that much about this stuff. correct me if im wrong

 

Yes the car starts to lean out if the injectors can not keep up. It also starts to break up up top as it can not sustain the amount of advance anymore either. Hence the 6* of knock you see at at the top of the gear.

 

im really glad i just bought some #60ers lol

 

Just get a nice tune for them and you will be all set.

 

Thanks for posting that up! I appreciate it .

 

ah i cant wait to get my 2.8 with 60s stage 2 belt and probably the ott ecu tuned with my mods . included to that my h.e installed then later on the dual pass and meth

 

So, question LSJ, Just to make sure that I am reading that right, the MAX RPM was 6984. MAX IDC was 115% on a stage 2 flash with the stage 2 hardware?

I am just trying to understand the mechanics behind the graph and the details associated with it.

Thanks for posting up the graph.

 

Yes 6894 rpms all stage 2, i believe this user had an intake as well. If you look at the log though you will see that by 6k rpms its already pver 100% duty cycle. After 80% you are along for the the ride.