[Camaro1973]

Hey guys, currently have a 19 ZL1 with a Magnuson 2650, Kooks 2" Headers, Green Cats, Borla Cat Back, 103 NW TB with the original 4' rotofab intake. I was thinking about getting the 5" big gulp as that's what they sell with the package I got but I already had the 4" and they said it was fine so kept it. (No cam btw)



Question is, would there be any gains if i was to put the big gulp on, (is it worth it) and second going from the 4" to 5" would it need to be retuned? Says you need a tune for the big gulp, but i am assuming that's coming from stock.


Thoughts?

[Joshinator99]

Depending on how hard you're pushing the blower, I'd guess there's 25-30 WHP available by going to the Big Gulp.

You will definitely need some tuning. The MAF scale will be off a good bit since the Big Gulp tube is a different diameter (5").

[Camaro1973]

Originally Posted by Joshinator99

Depending on how hard you're pushing the blower, I'd guess there's 25-30 WHP available by going to the Big Gulp.

You will definitely need some tuning. The MAF scale will be off a good bit since the Big Gulp tube is a different diameter (5").

I believe its just under 15psi if i remember correctly. It made 670rwhp which i thought was a bit low but he said the high system fuel pressure was dropping so didn't want to push it more. However i see people with same setup as me pushing 700 until fueling becomes an issue, so hes either playing safe or there's more power to be made.



At the moment i had to bring the car back because there's an issue with the mighty mouse and the valve cover combo they used. The mighty mouse is sucking up so much oil via the high vacuum and from the new covers its filling up so quick. Had a smoke screen other day when i started it, as the can was full and shooting oil right back into the intake. So dealing with them fixing that for now.


I guess the big gulp cant hurt as i will probably be putting a cam in it over winter.

[Joshinator99]

Originally Posted by Camaro1973

I believe its just under 15psi if i remember correctly. It made 670rwhp which i thought was a bit low but he said the high system fuel pressure was dropping so didn't want to push it more. However i see people with same setup as me pushing 700 until fueling becomes an issue, so hes either playing safe or there's more power to be made.



At the moment i had to bring the car back because there's an issue with the mighty mouse and the valve cover combo they used. The mighty mouse is sucking up so much oil via the high vacuum and from the new covers its filling up so quick. Had a smoke screen other day when i started it, as the can was full and shooting oil right back into the intake. So dealing with them fixing that for now.


I guess the big gulp cant hurt as i will probably be putting a cam in it over winter.

Sounds like they screwed up the MM install?

If you’re already out of fuel, adding the BG won’t help.

[laynlo15]

I don't think you'll see much if any gain with the 5" till your 750 or more rwhp. The 4" is a pretty dam good piece. What power are you at right now? I've been thru all the stages and I think 800 is a good number to switch to the 5". You can contact Mike at Roto Fab and I think you'll get the same info.

[Camaro1973]

Originally Posted by Joshinator99

Sounds like they screwed up the MM install?

If you’re already out of fuel, adding the BG won’t help.

That's what I said as well, but how the hell can you screw that up... lol


They said it was because of their low profile covers they use with the 2650 and the combo with the new mighty mouse and i didn't have a cam so it changes the vacuum. I don know, I just want it fixed already. As far as the out of fuel issue, that's what i'm not sure about. I know from speaking with others the high pressure may drop some, but its still in the safe area to push it. I'm just going to bring it to Julio at cartek once they fix the stupid catch can issue to retune it. He did my original tune and is probably one of the best.

[Camaro1973]

Originally Posted by laynlo15

I don't think you'll see much if any gain with the 5" till your 750 or more rwhp. The 4" is a pretty dam good piece. What power are you at right now? I've been thru all the stages and I think 800 is a good number to switch to the 5". You can contact Mike at Roto Fab and I think you'll get the same info.

670rwhp, no cam yet. I just ordered the big gulp from summit so i guess it can wait till i schedule a retune or is it safe to drive going from the 4" to 5"?

[Joshinator99]

Originally Posted by Camaro1973

670rwhp, no cam yet. I just ordered the big gulp from summit so i guess it can wait till i schedule a retune or is it safe to drive going from the 4" to 5"?

Just install the BG when you're at the shop to do the tune, it won't take long. Your drivability will be a mess without the tune, and I definitely would not go WOT until the tune is done.

[Road Pressence]

670 does seem low unless its like a mustang dyno or something. I'd try the big gulp and get a retune by another shop like you said, should be around 720-740 mark from similar setups I've seen. Goodluck and report back if you can thanks.

[JasonGofast]

It seems low considering when the 2650 came out they were showing cars with 700+ whp with only the blower and stock everything else.

That's a good package you got there. I'm actually getting the exact same set up minus the cats.

[Camaro1973]

Originally Posted by Road Pressence

670 does seem low unless its like a mustang dyno or something. I'd try the big gulp and get a retune by another shop like you said, should be around 720-740 mark from similar setups I've seen. Goodluck and report back if you can thanks.

Dynojet, SAE smoothing 5.

[Camaro1973]

Originally Posted by Joshinator99

Just install the BG when you're at the shop to do the tune, it won't take long. Your drivability will be a mess without the tune, and I definitely would not go WOT until the tune is done.

Yep that's exactly what i am going to do when it goes back to cartek.

[Camaro1973]

Originally Posted by JasonGofast

It seems low considering when the 2650 came out they were showing cars with 700+ whp with only the blower and stock everything else.

That's a good package you got there. I'm actually getting the exact same set up minus the cats.

Yeah this is what i dont understand, 2 shops told me once you get around 680 or so high side gets dangerous, but then i see people with 705rwhp with similiar setup (no cam). So dont get it. Maybe their dyno is a heart breaker....

[Joshinator99]

Originally Posted by Camaro1973

Yeah this is what i dont understand, 2 shops told me once you get around 680 or so high side gets dangerous, but then i see people with 705rwhp with similiar setup (no cam). So dont get it. Maybe their dyno is a heart breaker....

If you don’t do a voltage booster, then the low side drops out first. This can take out the high side very shortly thereafter. So, you have to datalog both of those plus injector pulse width to get a solid understanding of how your fueling is really doing.