Redefined1

iTrader: (1)

i just bought some #60 siemens injectors. i have a 2.9 pulley now, wondering if i should go with a 2.7 or 2.8. the only cooling mod i will soon be getting is a cobra h/e. is that sufficient enough for me to go with a 2.7 and keep my IATs cool? Also will the #60 injectors give me more hp even if i just stay with my current 2.9 pulley. (after my retune of course)

Bika

iTrader: (3)

2.7" creates too much heat and should have methanol/water injection. eaton techs will agree with this.

either go 2.8 or even keep your 2.9. the 60s will support the 2.9 better than the 42s will.

ShortStack

Well... honestly... id say it depends on how your gonna race it..

planning on back to back runs at a track, get a larger pulley.. untill you get more cooling mods.

if your just gonna do some highway runs / daily drive and not beat on it, id go with a 2.6 or a 2.7..

And the 60s will allow you to create more power, not so much making it.

Redefined1

iTrader: (1)

i only take it to the track when i do enough mods to make a difference in my track times. other then that its a daily driver/ some runs now and then

NVMYCOBALTSS

Puts flame suit on... 60s are overkill until you get into the 2.7 and lower rings. I have been running a 2.9 and will be running a 2.8 in the summer on 42's with the big cxr HE.

If you dip into the 2.6 or lower world, it is all in the tune. I have seen at least 2 balts in my area that were running 60's, 2.6's with all of the supporting mods and they took a **** within 2 weeks of each other.

Redefined1

iTrader: (1)

what do u mean, they blew there cars up?

NVMYCOBALTSS

one cracked a piston, one keeps blowing the dip stick out, the other has water in the oil.

Redefined1

iTrader: (1)

damn.... thx for the warning. guess ill stick with a 2.7. did they do alot of beating on it?

Zach06CobaltSC

First off you SHOULD NOT run anything lower then a 3.0 inch pulley on 42lbers. When you get into the 2.9 inch and lower pulleys on 42lbers your idc's shoot up so high that your injectors go static. Granted, you can tune a 2.9 pulley and 42lbers to make it "decent" however anything lower is unattainable. Coming from a TUNERS standpoint trust me on this one, you do not want to use 42lbers and anything smaller then a 2.9 that is WELL TUNED.

When your injectors are static your motor is not getting enough fuel. Starving your motor of fuel is a bad bad bad idea. Don't do it.

Now onto the op's question. I would personally stick with a 2.8 inch pulley until you have more cooling mods. When you drop below a 2.8 you put the blower out of its efficiency range and create a lot more heat. Dropping pulley sizes will add power, but it will add heat. If you don't have the cooling mods you will be adding to much heat and reducing your power after a single pull.

I personally recommend meth injection to anyone who is going to be doing multiple pulls on anything smaller then a 2.9 inch pulley.

Redefined1

iTrader: (1)

i dont want to sound arguementative so dont take this the wrong way but what i have read is that our superchargers max EFFICIENCY is our stock pulley at 12psi. so anything lower then 3.35 is already out of efficiency. if this is not true, just correct me. thats what i have personally read.

Zach06CobaltSC

Redefined1 - Don't listen to NVMYCOBALTSS as he obviously doesn't know what he is talking about. It's very possible that his friends blew up there cars as they are idiots, but I can tell you that it was not solely the pulleys fault.

When dropping pulley sizes you need to first off know what your doing, as it really helps. As I said above, running a small pulley requires a good tune and cooling mods. The cooling mods will help keep the iat2's down which will let you keep the power you have. When you use a pulley smaller then a 2.8 your putting the blower out of its efficiency range, however you can still make reliable power with methanol injection. You can use a 2.5inch pulley and create reliable power with methanol injection and a good solid tune, I don't recommend it on a daily driver, but its possible.

From reading all of these posts, I suggest you use a 2.8 inch pulley with the 60lbers. I am using the same thing, read my sig for all of my mods. You will notice a big power increase, especially if your tuned correctly.

Who is doing your tuning?

redefined1 - You must have misread. The stock supercharger, the m62 on our cars can support a 2.8 inch pulley at 7,000 rpm's. I will find the exact quote and information and post it up here as I don't have it off the top of my head.

Redefined1

iTrader: (1)

i am using one of my friends off another forum. he is local, he uses hp tuners. from what ive heard he is very good at chevy tuning. he also told me before he tuned my car he had just done 2 before me that same week. he runs a shop called "all out performance"

Zach06CobaltSC

Great! Hptuners is a wonderful program, its the same I use to tune my car and others. If you need any help let me know as we are not that far apart =D.

NVMYCOBALTSS

See what I meant by flame suit...

If you are going to claim 42's go static with anything lower than a 3.0, tell the whole story about it. They will typically go static at 100% throttle in the upper rpm range. On a daily with just a few pulls in normal 60 degree + weather, you shouldn't have an issue unless you beat on it like a cheating wife.

Zach06CobaltSC

Also redefined1 here is a direct quote from rali who is a very knowledgeable person here.

2.7 pulley will put you at the m62's max 16000 rpms at roughly 6875 engine rpms. after that, you are overspinning the blower and making tons and tons of heat.

2.6 pulley will put you at the m62's max 16000 rpms at roughly 6600 engine rpms. after that, same scenario, overspinning and tons of heat.

Redefined1

iTrader: (1)

actually he is right about the 42`s going static. i posted a couple times about this when i chose my 2.9 pulley and 42`s. i was told 2.8 and 2.9 pullies do push ur IDCs past safe levels. safe being 80%.

Zach06CobaltSC

NVMYCOBALTSS - 42lbers will go static on a 2.9inch pulley in the higher rpm's where you need the fuel the most. I am not "claiming" that this happens, it DOES happen. If you would like proof I will post an HPtuners screen shot, or a log of 42lbers going static on a 2.9inch pulley.

Redefined1

iTrader: (1)

i have a shift limit of 7,000 rpms but since im running my 2.9 with 42`s i usually go ahead and shift at 6,500. so u think i would be safe with a 2.7???

Zach06CobaltSC

Redefined1 - exactly, 80% is what most tuners try to stay under, however if it is slightly over its not a big deal. When using 42lbers and a 2.9 inch pulley I have seen idc's well over the 110% mark which IS static. Luckily you have enough wisdom to know that you need 60lbers .

Redefined1 - if you are going to get more cooling mods, more then just the heat exchanger go with the 2.7 inch pulley. If you are not going to get more cooling mods, especially meth, then stick with the 2.8 inch pulley.

NVMYCOBALTSS

Where did I say it was the pulley's fault? I thought I stated it was in the tune?

Yep, there it is...

Zach06CobaltSC

Redefined1 - Also make sure you shift at 7k on the 60lbers and the 2.8 inch pulley as these cars pull very very strong all the way up through the rpm band. I know of a lot of members that push 7500 rpm's on stock valves and springs. I personally "generally" don't go past 7,000 rpm's because its my daily driver. However come this summer at the track I should be pushing 8k rpm's with a fully built top end. PnP heads, springs, valves, retainers, forged pistons, etc.

NVMYCOBALTSS

I will completely agree with the valve train comments. It is not a honda....

Zach06CobaltSC

NVMYCOBALTSS - I never stated you said it was the pulleys fault. I was saying in general that it is NOT the pulleys fault that the car "broke". Also you state if you "dip into the 2.6 or lower, its all in the tune". Whenever you run a smaller pulley, it is ALL in the tune. It's always the tune that makes it or breaks it with these cars. If you have a bad tuner, your going to have a bad car. Period. If you have injectors going static, excessive iat2's, and your doing multiple pulls you will blow something, more then likely the #4 piston.

What I was stating you shouldn't take offense to. It's just plain stupidity to run 42lbers and a small pulley. Who wakes up and says "hey guys I have a wonderful idea, lets tell people its ok to run 42lbers and X pulley so they can starve there motor of fuel and have static injectors". Its stupid.

NVMYCOBALTSS

Post up the injector log... I am curious as to TPS, RPM and Load demands when 42's go static.

Zach06CobaltSC

I will post up a screen shot from hptuners and upload it so everyone can see that 42lbers go static around the 6k mark on smaller pulleys.