v7 ysi not making boost
v7 ysi not making boost Like the title says I have a v7 ysi and its only making 6-7 psi (77 kpa 2 bar map) by 6k rpm. I'm running a 7.8 crank and a 2.95 blower. I have a fmic and triple checked all my hose clamps. Any idea what's happening?
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
Was the unit new or used ? And does it look in good condition ?
Also, at idle, how much air is getting dumped out your BOV ? It should be quite a lot.
I assume your HPT log does match gauge pressure ?
Not sure what way HPT works, but normally 100kpa is atmospheric with most other ecus.
Ive only ever come across one system that treats 0kpa as atmospheric.
So are you sure your MAP sensor is scaled correctly ?
Also, at idle, how much air is getting dumped out your BOV ? It should be quite a lot.
I assume your HPT log does match gauge pressure ?
Not sure what way HPT works, but normally 100kpa is atmospheric with most other ecus.
Ive only ever come across one system that treats 0kpa as atmospheric.
So are you sure your MAP sensor is scaled correctly ?
Its new. and yes at idle its like a leaf blower. I'm using a 2 bar map so at 50 kpa that is atmospheric pressure and 100kpa is 14 psi and I do have it all scaled in the tune. My log matches my boost gauge.
Correct length belt? How much dust is on the pullies? It should be making a lot more boost than that with your pulley combo. Have you checked to make sure nothing is blocking the intercooler?
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?
Pouria Savadkouei
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo I'm betting the belt is slipping. That is not near enough tension for a YSi.... You should see a vette's YSi set up. They have CRAZY belt routing and tension (a automatic and manual tensioner) along with a couple idlers and even they'll slip then with that size pulley.
It could be slipping enough that there isn't enough traction to shear the belt, therefore no dust..
It could be slipping enough that there isn't enough traction to shear the belt, therefore no dust..
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
On the kpa scale, 0kpa should be absolute vacuum. 100kpa is atmospheric. 200 kpa is 1 bar positive pressure, ie 15psi boost gauge, and 300kpa 2 bar, ie 30psi boost gauge pressure ( approx )
So engine off, key on it should read 100kpa, or pretty damn close to it. The only anomoly is some ecu's treat atmospheric as 0kpa, which is technically wrong. But they would then treat 0 to -100kpa as vacuum. Which is wrong, but in some ways it can make sense.
So then 100kpa would be 1 bar gauge pressure, ie 15psi boost gauge.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
The setup looks fine, but hard to tell how much tension you have there. What make belt is it too ?
Can you alter the idlers etc to force more wrap around the pulley ? Is that a 6 rib or 8 ?
IMO if it was slip, I still think you would see boost rise, then either level off or fall as revs rise.
Can you alter the idlers etc to force more wrap around the pulley ? Is that a 6 rib or 8 ?
IMO if it was slip, I still think you would see boost rise, then either level off or fall as revs rise.
With a stock pcm in a lt1 you have to trick to computer into seeing boost. So you will have to install a 2 bar map sensor and scale the tables by half. So my sensor reads 50 kpa at atmospheric pressure and 100kps at 14psi. The tables in the factory pcm will only read up to 100 kpa.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
With a stock pcm in a lt1 you have to trick to computer into seeing boost. So you will have to install a 2 bar map sensor and scale the tables by half. So my sensor reads 50 kpa at atmospheric pressure and 100kps at 14psi. The tables in the factory pcm will only read up to 100 kpa.
No problem, that makes sense.
Cheapest option is get a Gates belt, and tighten the **** out of it.
Even spraying some hairspray onto it before making a pull might make a difference ( it's sticky stuff )
If you're relying on an auto tensioner making enough tension, I'd be dubious unless it was installed tensioner right to its limit.
Try moving the lower idler closer to the blower to force more wrap. It might also then allow more tension on the belt before the two sections make contact.
But really, nothing with the setup looks bad. It all looks quite capable of working.
Ok I'm going to try tightening the belt. the only other thing I can think of is maybe some jackass stuff something in my intercooler when I wasn't looking . I am installed the intercooler on my driveway so it was outside open to the public for a while