venomws7

What's up everyone ?

Received the new pulley & dewitt radiator from BLOWNBLUEZ06 (Thanks buddy) a couple of months back and my friend is finally ready to install them

I have a Couple of questions:

Estimated boost gains from the pulley swap?
We are seeing between 17-18psi around 7k rpm

Estimated HP Gains from the pulley swap and going from 91 octane + straight meth to C16 Fuel + straight Meth ?

We're now at 805rwhp with VERY VERY Safe tune with 91octane + Meth
*17 timing high 10s A/F Ratio.
I told him I'm expecting 940-980rwhp with the new pulley, Race fuel/Timing does that seems realistic ??

It's 408ci 9:5 Comp
AFR 225 Heads
Blower cam.
Full Exhaust
6 Speed C5Z

What do you guys think? Any suggestions or recommendations ?

Sam.

Milan

3-4 psi if I had to guess. I think 950-1000 whp is what you will get...I think the Ysi is way out of its efficiency range with the 2.75 pulley. Still makes good power though...

NVTHIS

I say somewhere between 935-955 rwhp. I say about a 4psi increase.

zrtman1

What pulleys are in a Ysi's efficiency range?

MVP'S ZO6

I think you will be at 20+ psi and 950+ with pump gas and meth.

winters97gt

Do you have personal track times to verify this? 2.85 puts the YSI in its sweet spot given the impeller speed on an 8 inch crank. Just looking for racing proof, not dyno's since my C5 trapped very well on 91 pump with a 2.85.

venomws7

Thanks for the info guys looking forward getting the car done.


I wish we had some good pump gas here
With the new pulley we're going with race fuel and hopefully it will help even more with power gains + meth

c5mtl

I made 1014 with a 408 and 2.75 ysi at 21 psi.....I think the dyno was a bit happy but I did trap 157 at 3650 lbs race weight ...oh ya...always on c16

venomws7

Auto or manual?
Those are awesome trap speed
I'm sure the owner of the car will be happy with anything over 950rwhp traction will be a major issue with his 18s but we will see how it goes form 3rd gear.

lsxvette

every .1 pully size is 1psi of boost

c5mtl

Auto.....I had a couple more mph in it ...one of my pipes blew off at the 1000 foot mark......oh ya that's on 15inch m/t pro radials

Milan

I know this because I have dyno'd my car a lot with multiple pullies while keeping the rest of the setup the same. Once you hit 2.95/8 the returns are severely diminished.

Ksths2

I was 1010rwhp @ 6500 890tq @ 21psi with a 2.75" - 408 & E85

venomws7

Compression, H/C/I And trans?
Great numbers

Ksths2

10.5:1, LSA, Custom cam, Holley hi-ram - RPM Level 7 4L60e

a/c man

nice who tunes your car

winters97gt

I guess that 8 second pass with a 2.75 pulley done below could be accomplished with 4-5 pounds less with a 3.125 that Ksths2 just ran? No, it wouldn't. Your world is on the dyno. Not the track. My 2.85 trapped very well in the 1/8 mile on 91 pump. I'll be interested to see how it runs soon with a new engine.

Ksths2

Speed inc in Chicago

robert miller

The YSI loves the 2.75 pulley if it does not slip on you you going to love it. 21psi and 965 rwhp..

Milan

If we are bench racing trap speeds then what documented trap speed increase have you seen going from 3.125, 2.95, 2.85, 2.75? Do you have this data or are you just conjecturing like usual?

IMO the 2.75 might give a small bump in midrange but I don't see anything posted in this thread that makes me believe there is a noticeable gain over my 2.95.