joe88

Hey everyone, I have a 2006 cobalt ss/sc. Original 60km. I have purchased a zzp pulley 2.9 and belt based on my talk with them. However I contacted their non ebay store and he is telling me that the 2.9 is way too low to use on 91 octane. I have headers and offroad downpipe waiting to go on. Would I be better off returning the 2.9 and running the 3 or 3.1? I plan to purchase dual pass and make an opt b. If I go with the 3 should I use the 42lb injectors? I am looking for a bit more go power but also want to maximize fuel economy. . I have hptuners as well. Is there anyone who remote tunes the lsj? I will be purchasing a wideband for a/f. Thanks for the help.

keiserX13

iTrader: (3)

their site tells you what mods you need to support each size pulley they offer

keiserX13

iTrader: (3)

From https://zzperformance.com/ecotec/pul...odular-pulleys

joe88

Wow reading comprehension fail. I saw that before and for whatever reason the top line didnt register correctly. At this point am I better off to return the pulley? Would I be better off with the 42lb injectors and 3.1 or the 3.0 and 60lb, if I am looking for power and fuel economy?

Stumpalump

At sea level in a hot climate a 3.1 is safe. Sea level to 5000' in cool Canadian air a 3.0 sounds right. Above 5000' elevation then keep the 2.9. 42's for sure. I'd add the ZZP ignition coils and dual pass end plate as well to keep it efficient. Beat the snot out it and not worry about sucking gas, pulling timing or blowing it up that way. Canadian gas is expensive.

joe88

I am only at 670 feet above sea level and Southern Ontario air often gets stupid hot in summer for a bit. Ill have to see what zzp says I can do for exchange.

Johnny Bliss

i'm running 42lb injectors and 2.8 pulley. other mods in sig.

all you need is enough fuel to go with the air, you can heat soak bad if you road race the car or whatever...

get 60lb injectors and you can easily run the 2.9 pulley

Johnny Bliss

they're just trying to get you to buy more stuff.

jmix

iTrader: (2)

I've read where some people ran 42s with a 2.9 with no problem and others say you have to run 60s. All in all I believe it comes down to the tune.

Johnny Bliss

Been running 42s and 2.8 for 100k miles.

The injectors go static at very top of rpm range but it's not lean. No timing is pulled.

If you're buying it all right now, buy the 60s over the 42s. But I'd you already have 42s you can run a smaller pulley.

But buy the 60s over the 42s

jdbaugh1

iTrader: (1)

I don't think OP has bought the injectors yet. Definitely go with the 60's. 42's may barely do it but you have way more head room with 60's. The only disadvantage of 60's over 42's is that they may be a tad bit harder to make idle nicely though it can be done. That considered there is really no good reason to get the 42's over the 60's.

Henry3959

Is this a typing fail?

60 Kilometer / 37 miles?

jdbaugh1

iTrader: (1)

I think he meant 60K miles though it is hard to say for sure.

Henry3959

He's from Canada "A"

Henry3959

How are you measuring this?

jdbaugh1

iTrader: (1)

Well nvm then lol. I'd be amazed if it really only has that many miles.

Slowbalt2000

iTrader: (1)

His injector duty cycle is likely over 100%

Johnny Bliss

Yeah exactly. It hits 100% around 6500 rpm

joe88

Sorry apparently a typing fail as well 60,000km. Picked up at 52,00km. I have not purchased injectors yet. I thought I had read there was issues with the 60lb injectors and defco. Would you guys return the 2.9 if you didnt have solid access to 93 octane?

chevygirl2006

That isn’t even true

Henry3959

If you want to add more go fast parts down the road, get the 60's now. I tuned my engine with 60's on the stock pulley and still have them with a 2.8 pulley. You do not want to push injectors past their ability to properly meter which is around 80% DC for most. When an injector pintle begins to float or bounce, the command and output are no longer in sync.

joe88

3.35" pulley - Stock OEM size

3.1" pulley - 42# injectors

3.0" pulley - Stage 2 Kit, ZZP Down pipe, 93 octane.

2.9" pulley - Stage 3 Kit, 60# injectors, Dual Pass End plate, Header/Down pipe, 93 octane.

Hmm so if I got the dual pass and I would be ok to run the 3.0? Would I make more power on the 3.1 with 91 properly tuned or on the 3.0 tuned for 91? Is the extra cost worth it over the 3.0 when considering 91 octane?


Car is just used for back roads and daily driving. Honestly I was just hoping to make the car a bit more fun and possibly get better mileage. It was just such a disappointment coming from a 2010 turbo cobalt on 23 psi. Not sure I want to deal with the IAT issues with the smaller pulleys. I appreciate everyone's responses. Car is clean so I figured it would make a great base to mod.

Anyone have anything to say about the spray pattern of the 60lb seimens as mentioned in the fuel injector article? Anything to worry about?

Johnny Bliss

Iat is only a problem if you hammer on it over and over.

2 octane is very little difference and those octane rating are averages it's not guaranteed.

Buy some 60s a dual pass and a 2.8 and call it good

jdbaugh1

iTrader: (1)

The spray pattern of the seimens is not ideal but it also doesn't seem to cause people many issues. However if you want a split spray injector check these out https://fuelinjectorconnection.com/c...ltivalve-heads Those are what I run in mine.

Henry3959

The only difference is in cold engine emissions from start up to warm up. I don't think there is anyone on here that cares about their emissions at any time based on all the cat-less downpipes installed.