From knowing nothing to having a Thunderbird supercharger on an m20b27i

[whodwho]

Or belt slip

[The Dark Side of Will]

I feel like if I pulley it up, it would just make more boost earlier and trail off earlier. Or am I just witnessing my engines' volumetric efficiency by way of my boost gauge?

Combo of both, possibly with some belt slip thrown in. Spring tensioners really are best. Also, the high power M90 guys have to go to 8+ rib belts and a LOT of wrap on the tiny pulleys to avoid belt slip.

So if it peaks at 12 and tails off to 10 at redline, that will still be more oomph than peaking at 7 and falling to 5 at redline.

[Ether-D]

Or belt slip

This is possible.

So if it peaks at 12 and tails off to 10 at redline, that will still be more oomph than peaking at 7 and falling to 5 at redline.

True, but it's scary enough for me now...

[LJ851]

Or belt slip

Or an air restriction in the intake system somewhere, like the intercooler or that 180 degree bend. I think this is most likely.

[The Dark Side of Will]

Just for the summer while I build the 2.8 out of the block from the 87.

Here's a budget 3.0 M50... can probably come up with something simlar for the M20.

http://www.r3vlimited.com/board/showthread.php?t=283320

[Q5Quint]

Me this upcoming weekend:

[Ether-D]

Quint, that looks great! How did you possibly keep power steering (sarcasm font needed)? Go get it bro!

[Lithium]

slip

I may after I get another DD, but for now, this one has plenty of power. Also since it builds the boost up to 7 and then trails off, doesn't that mean I'm already in the "efficiency island" of the m90? I feel like if I pulley it up, it would just make more boost earlier and trail off earlier. Or am I just witnessing my engines' volumetric efficiency by way of my boost gauge?

Belt slippage is likley the cause - I am running a six rib belt with a manual tensioner + huge tension & it works great. (M50 + Eaton M90)
Boost stays consistant all the way to Redline.

When I started out I thought my engine was sucking up the boost @ high rev's but it was just belt slippage.

I hope this helps.
Tim.

[Ether-D]

Belt slippage is likley the cause - I am running a six rib belt with a manual tensioner + huge tension & it works great. (M50 + Eaton M90)
Boost stays consistant all the way to Redline.

When I started out I thought my engine was sucking up the boost @ high rev's but it was just belt slippage.

I hope this helps.
Tim.

Yep, it is slipping. I was watching closely today and as soon as boost starts to drop, I can hear some squeekage. I had convinced myself it was the alt belt because before I put the sc on, it would start slipping at high rpm. I also have a manual tensioner, but with normal tension on the belt.

Tim, on yours, was it the sc pulley slipping or the crank pulley? I have pretty good wrap on both. Also, what sc pulley is on yours? Mine is off of a later model supercoupe so it's the biggest one that fits this m90.

[Lithium]

Tensioner

- It usually always slips on the blower pulley.

My SC pulley is from an early Supercoupe (I think)
SC pulley diameter is 3.15" - crank is 5.5" - Making 5.5PSI on my M50
(Next I will got to 7" on the crank pulley & hope for 10.5PSI)

Have a look at my photo below.
Things that worked for me is having about 65% wrap around the SC pulley - using the tensioner position to increase wrap - my tensioner is manual & I preload it up with a jack - if I can turn the belt more than 90 deg it's too loose - I have about 8/10K on the belt. I have adjusted it a couple times & it's not slipping yet.

I hope this helps.

[Ether-D]

I only have 50% wrap on the s/c pulley. I added more tension to to the belt and it didn't change it a bit. I was thinking about trying a 7 rib belt. Only problem then would be that I'd have 1 1/2 ribs not touching the crank pulley. But since it's likely the s/c pulley is slipping, it could still benefit me about 14% more gription.

[Lithium]

I only have 50% wrap on the s/c pulley. I added more tension to to the belt and it didn't change it a bit. I was thinking about trying a 7 rib belt. Only problem then would be that I'd have 1 1/2 ribs not touching the crank pulley. But since it's likely the s/c pulley is slipping, it could still benefit me about 14% more gription.

I made my own crank pulley by using a six rib pulley we had lying around in a box of junk and making the inner part to bolt onto the crank and welding them together. (See Piks) it really helped / now I need to find a 7" 7 rib pulley & do the same to add more boost.

[Ether-D]

I got off my ass and put the 3.73 lsd back in today. I was kinda nervous about it. I was afraid it would lose all the big balls. It's just fine. It seemed to sustain more boost. I saw it go over 7psi (barely) for the first time ever. I reckon I might even get back some MPGs. I got 20 mpg last tank.

Also re-did my pin stripes in an A/C Schnitzer sort of tribute in burgundy. I think it's titties.

[Q5Quint]

take your top off.
Show me them pin stripes.

Now I am trying to figure out some crazy tensioner situation, but I should have like 50%+ wrap without it. I went with the custom pulley but added in a vgrove for the ps, but in doing so had to delete the stock mechanical fan because of it pushing it all forward.

[Ether-D]

A/C Schnitzer inspired pin stripe.

Quint, what size are your pulleys?