CALL911

iTrader: (17)

Just as the title reads.

If you have a maxed out D1SC, please answer the poll on where your max boost level is. Feel free to give vehicle info in a post.

BigBadWhitey

iTrader: (3)

Very interested in numbers, if people could post engine size as well as boost number in the comments possibly as well?

CALL911

iTrader: (17)

There is a lot that plays into it past getting the appropriate pulley size and running the numbers to knowing you are maxed out at a certain RPM.

Shoot, I gained 5 pounds of boost and 100 RWHP just by changing to a different blower inlet and larger air filter.

The Alchemist

iTrader: (19)

Exactly... there are a number of different factors that dictate how much boost you actually see from a supercharger. How good if the inlet to the blower, how well does the charge pipe flow, what's the engine specs including cam size/overlap as well as cubic inches, and exhaust.
Back when I had a 4.00" blower pulley, with a 7.65" crank pulley, I saw a consistent 15-15.5psi at 6800rpm which is 53,000 blower rpms. Now I recently swapped to a 3.4" pulley, so I hit that same blower rpm at roughly 5200rpms. Only problem is my proflo bypass valve and IAT sensor were both leaking badly so I got boost fluctuation above that point.

Once those are fixed, I should see a solid 18-19psi at 6800rpm and max blower rpms.

Detoxx03

iTrader: (14)

Mine isn't maxed out but I'm making 770rwhp on 10psi. Running a 4.5 blower pulley and 7.530 crank pulley. Revving to 69000 so that's 47,388.60 out of a possible 62,000. Slo-Poc will know soon since he's running close to the same setup.

At the end of the day the boost number doesn't matter. If your setup is efficient and making power that's all that matters. I'd rather make the most I can make with the least amount of boost.

CALL911

iTrader: (17)

I'll be interested to see the difference Alchemist.

Lots of things have surprised me. The biggest one was gaining that much power and boost just from swapping out the small plastic inlet tube and air filter that came with my D1SC kit for a custom metal one and larger filter.

Since boost is a measurement of restriction, I also expected to see a drop in max boost when I swapped heads from my AFR 180 heads to the much larger AFR 227 heads. I still don't really understand why, but after I swapped heads, I didn't loose any boost (but I gained 85 RWHP).

The Alchemist

iTrader: (19)

Here's a graph I made of my boost vs. rpm when I dyno'd my car, and you see how the boost was nice and smooth till about 4800rpm which is when I hit ~14-15psi and my bypass valve was leaking badly at that psi.

Ls3 slo-poc

Ls3 with ls9 cam on an a&a kit making ~9psi made 652 with a mn6. 4.5 pulley stock crank. New setup will have a 4.0 or 3.8 with a 8%over drive (7.95) crank. Spinning it to 7000 rpm.

Exidous

iTrader: (11)

The answer to your RWHP gain is pretty easy actually. More CFM. Your boost stayed the same but your CFM went up. Similar to going to be bigger turbo on the same wastegate spring.

CALL911

iTrader: (17)

I fully understand why I made more power. That was never in question. What I don't understand is why with much less restrictive heads that I didn't loose any boost.

The Alchemist

iTrader: (19)

That's simple, because your heads weren't the source of the bottleneck in your setup. It could have been the cam, maybe the exhaust, who knows, but it wasn't the heads. Maybe it's your intake manifold.

sbcgenII

iTrader: (1)

If he picked up 85rwhp then the heads were some source of restriction.

sbcgenII

iTrader: (1)

Same pulley? Intake? same temp outside? same chamber cc? Same valve springs? Same exhaust? Same intercooler? New belt?

CALL911

iTrader: (17)

You hit the nail on the head. I have a very large cam, very non restrictive sheet metal intake, maxed out on pulleys, biggest air filter that can fit, I didn't change anything except the heads. The previous combo had been in for a while on a couple dyno's. Even the tuners agreed that the single point of restriction was the baby AFR 180 heads (which was why I wanted to make the change to the larger AFR 227 heads as everything was pointing to the AFR 180's being the choking point). In the end, it was proved they were. The peak power changed big time between dyno's and sure enough 85 RWHP with the only thing changed being the heads (both tuned in very similar temps and conditions).

And yet, no loss of boost after swapping the heads. I thought for sure I would loose at least a pound or two. But sure enough, I see the exact same 15#'s I saw before.