Supercharger and Timing

[tjh566]

Ok, So im gonna put a custom application supercharger on my car and Im gonna put my base timing back down to 9/10*, Do I need the Msd Boost Retard Unit for just 6 psi of boost or should I be fine? Also, Do I need a bypass valve for this low of boost?

 

[69clark]

Basically from what I have read, it isn't mandetory for either of those items but I will help. My car ran 6lbs and didn't have a bypass for 3yrs. The boost retard depends on alot of things but if 9-10 is too much, you will just have to back your dizzy down.

I now see your doing an M90 eaton, the bypass needs on that may be different, I was comparing to a centrifugal sc. So now I must say I am not sure on the bypass valve.

 

[tjh566]

6 psi is 6 psi right? or no?

 

[69clark]

Well I am not 100% sure because you are boosted after the TB where I am boosted before the TB.

 

[tjh566]

Im still learning all this supercharger stuff, So if you could enlighten me as to why there would be a difference, I know the superchargers have different rotors and such but ???

 

[JimBowy]

when you read my answers, keep in mind i run a m90 + 5.0L on my car

you wont need the boost retard (but its never a bad idea to have one)

seeing as your going for a m90 tells me your obviously interested in saving some $

I would suggest using the bypass however. Use the Eaton bypass for the M90s. I use a bypass from the t-bird supercoupe.

 

[tjh566]

I have the by-pass sitting here off of a T-bird, Just wanted to know if i need to fab it in or not.


btw, are you using the stock pully that came on the T-bird supercharger, if not, what size is it to run 6psi?

 

[cbarr300]

If I'm not mistaken, Boost is actually a measure of resistance. If your engine flows more air...then ur gonna see less boost but not necessarily less power. If ur heads and exhaust are restrictive then ur gonna see more boost but not necessarily more power. It's kinda like the horsepower/torque thing. You may have a good horsepower #....but the torque is what gets you goin......You may have a good boost #, but what you can flow is what gives you the extra hp/tq.

Think of it as blowing into a straw. If the straw is small in diameter then you have to apply more air pressure to get it through the straw. If the straw is larger in diameter then that same amount as you applied before goes through with no problem at all which would register as less boost since there's less resistance

sooo....6 lbs isn't necessarily 6 lbs. This is the way I see it nehow.

 

[JimBowy]

I have the by-pass sitting here off of a T-bird, Just wanted to know if i need to fab it in or not.


btw, are you using the stock pully that came on the T-bird supercharger, if not, what size is it to run 6psi?

i have a pulley much much smaller than the stock t-bird s/c pulley
its barely bigger than the shaft diameter

what crank pulley will you be using?

 

[JimBowy]

also, what generation blower is this? does it have the coated rotors? are you using stock heads? what fuel system?

what fuel do you plan on running? will you run an intercooler?

 

[JimBowy]

also, what generation blower is this? does it have the coated rotors? are you using stock heads? what fuel system?

what fuel do you plan on running? will you run an intercooler?

 

[tjh566]

No intercooler, FMU 10:1 with a t-rex pump, stock heads, gt40 lower intake, full exhuast, not sure on generation, stock crank pully, rotors dont appear to be coated but it was just rebuilt with new rotors.

 

[OrangeMustangGt]

you could always run locked out timing. I would be a bit scared of running nothing because our car's ecs advance timing so much. i vote go with a boost retard or a custom chip, tuning, etc to do the same thing.

of course you can always try it without....set it to about 8, then take it for a ride and let off quickly if you get knock......then pray your headgaskets held.

oh, and i heard that those m90s put out some serious heat....so with that in mind i would DEFINATLY not let the computer advance like it wants too.

 

[final5-0]

If I could add just a bit more here I would say I agree with Kyle about wanting to be cautious about too much spark

He advised to dial it back a bit and I would say a couple would not hurt
and
Maybe even to start out ...... less ....... a good bit less

I looked at the stock GT spark table and here is what I saw.

At around 85% to 100% max load or wot, you will be seeing 21 to 26 degrees from the pcm in a rpm range from 2K to 5K

At around 50% or mid load ... it even goes higher
1500/32 ... 2000/34 ... 2500/37 ... 3k/35 ... 4k/35 ... 5k/35

If you set your dizzy at 8 ... then you would do the -2 thing to all those above values btw

Keep in mind these values could + or - a bit depending on ............
various things but still ............
You can now see why Kyle threw up the ... red flag of caution

With a fmu ... the ratio is anybodys guess at times

I would dial back more spark!
I would dial back more spark!
I would dial back more spark!

One more thing you might wanna consider ..............

Dialing back more spark!

If you are at a mid load driving condition and then nail it .............

It don't instantly go to the lower max load spark values

At first ... SCREW THE POWER

Get stuff all set so you don't have to become .............

A SBF HG Changing Expert

Forced Combos can pop em quick ... REAL QUICK

Just a little heads up info
and
I look forward to seeing what you come up with
so
Let us know all about it

Grady

 

[Stanger007]

I'll agree with Grady on making sure that your timing is safe. I just bought an S-trim and have been doing some research on the tuning aspect of it all... boost + high timing will break stuff amazingly easy.

Good luck with your build - keep us posted.

 

[JimBowy]

I can testify to the hot temperatures. My M90 blower would produce 270*F air at WOT. When I ran 93 octane pump gas even with 6* base timing I would hear constant detonation.

To solve the problem i ran 110 octane Turbo Blue @ 8* base. No more detonation though with today's gas prices that will get expensive quickly.

 

[Mustangless]

It would probably be cheaper to get that snow performance thing. 270* is really hot.

I can testify to the hot temperatures. My M90 blower would produce 270*F air at WOT. When I ran 93 octane pump gas even with 6* base timing I would hear constant detonation.

To solve the problem i ran 110 octane Turbo Blue @ 8* base. No more detonation though with today's gas prices that will get expensive quickly.

 

[tjh566]

Ok well after reading this I just ordered the MSD Boost Timing Master, It will decreace total timing by 1-3* for every pound of boost, so 6*3=18* of Retard.. Should be safe there

 

[JimBowy]

Ok well after reading this I just ordered the MSD Boost Timing Master, It will decreace total timing by 1-3* for every pound of boost, so 6*3=18* of Retard.. Should be safe there

i'll repeat my question before you keep going,
what is your goal here? why are you using the m90? is it primarily a finanical decision (cheap HP)?

 

[JimBowy]

stock crank pully

so your going to run the supercharger with the accessory 6-rib belt?
have you bothered working out the speeds the blower will be spinning given the diameter of the crank pulley and the supercharger pulley?

im not sure you understand how much work your getting yourself into