August MM&FF - S/C with a Wastegate

[StangIT]

WOW!... Did you guys read this article?
It's such a simple idea, has anyone done this before!?

To put it as simple as possible, it allows you to put the smallest pulley on the blower for maximum boost and then you use the wastegate to dump unwanted boost.

So if MAX boost is 16lbs... you could set your wastegate's max setting (CLOSED) to run this level... THEN, when you wanted something more dossile for street use, you simply flip the switch and set the wastegate to dump, say... 4psi, leaving 12psi. AWESOME!


DISCUSS!

[Iceman]

very cool idea ,i always wondered if anyone would fab one up

[dontmockthemach]

Have a link? I think I might do that for my car. Wonder if it takes special tuning, or replaces the bypass valve?

[StangIT]

[StangIT]

What this means to me is this...

IF I were to install a P1SC Procharger head-unit with a pulley that sets the MAX boost at 8psi, I would get a whopping 400 some-odd HP and TQ at around 6,200 RPM.

IF I were to install this same head unit with a pulley that sets the MAX boost at around 12psi and use a waste-gate to dump the excess boost, I would get those same or even better HP/TQ numbers at a much lower RPM!...

[cobramach1]

Very interesting. Though I like the quick takeoff of the superchargers, I'm still more of a fan of the turbos myself as they aren't as hard on the engine for every day driving. I went to the turbo people website and one of the customers cars runs a 7.65@190mph on drag radials with a turbocharged mustang of our body style. Very impressive.

[StangIT]

Originally Posted by cobramach1

Very interesting. Though I like the quick takeoff of the superchargers, I'm still more of a fan of the turbos myself as they aren't as hard on the engine for every day driving. I went to the turbo people website and one of the customers cars runs a 7.65@190mph on drag radials with a turbocharged mustang of our body style. Very impressive.

YEAH... That's a FAST Cobra!

[cmylxgo]

There are trade offs...and I have played around with this in the past...the smaller the blower pulley the more HP it will cost to spin the blower.

Lets say you run a 20lb pulley and open the waste gate at 10lbs you will make 500hp. If you were to run the 10lb pulley and not open the waste gate you will make 550hp. However, the power curves will look alot different. The 20lb pulley will make the 500hp much sooner in the rpm range because boost will build much faster and power will not rise at the same liner rate as it would if you ran just the 10lb pulley.

This is a great idea for those out there that want an easy way of going from 10lbs to 20lbs without having to spend all that time swapping blower pulleys.

My current setup is different, but uses the same logic about reducing boost on pump gas. Since my car is an auto and is controlled by the computer my street tune shifts the car at 5500rpm. At 5500rpm my car only makes 15lbs of boost. I reflash with my xcal to my race tune and now my car shifts at 7000rpm and makes 20lbs of boost.

-Corey

[DSG Mach ONE]

I talked to Jim Summers @ ProCharger last year about doing this and he told me it would be a bad idea... basically you will be spinning the blower alot harder creating more hot air and putting the blower out of its efficiency range.

A better idea would be to put the smallest pulley you want on the car for the track with race gas, but on the street keep the rpms lower like Corey said, and use less timing in your tune.

[65fastback2+2]

Originally Posted by StangIT

What this means to me is this...

IF I were to install a P1SC Procharger head-unit with a pulley that sets the MAX boost at 8psi, I would get a whopping 400 some-odd HP and TQ at around 6,200 RPM.

IF I were to install this same head unit with a pulley that sets the MAX boost at around 12psi and use a waste-gate to dump the excess boost, I would get those same or even better HP/TQ numbers at a much lower RPM!...

exactly....a couple of my local buddies use this same method. near-instant boost is awesome

[juno]

It may be called a wastegate, but in application it is an adjustable blowoff valve.

It may not be for everyone, but I am sure in some applications it will be acceptable. You would not have to drop to the lowest pulley available.

[Bullitt5094]

Two questions. First, if this is a draw-through MAF application, how do you keep the tune correct with all that metered air escaping into the atmosphere? I can only see this working on a BT meter which are a pain to tune for the street.
Secondly, all this really does is make a Centi blower act like a PD blower. Just install a KB or something.

[INDY]

Originally Posted by DSG Mach ONE

I talked to Jim Summers @ ProCharger last year about doing this and he told me it would be a bad idea... basically you will be spinning the blower alot harder creating more hot air and putting the blower out of its efficiency range.

A better idea would be to put the smallest pulley you want on the car for the track with race gas, but on the street keep the rpms lower like Corey said, and use less timing in your tune.

A few of our customers had us do this for them, they are now referred to as "Street Sweepers". They tend to blow a ton of air out from under the car, LOL. We use BT set ups at the shop, so its fairly easy to tune around.

I WOULD NOT ADVICE DOING THIS, its not worth it just do as recommended in the quote. It will reduce the life of your blower, and create a higher average intake air temp.

[01TruBluGT]

Originally Posted by cmylxgo

There are trade offs...and I have played around with this in the past...the smaller the blower pulley the more HP it will cost to spin the blower.

Lets say you run a 20lb pulley and open the waste gate at 10lbs you will make 500hp. If you were to run the 10lb pulley and not open the waste gate you will make 550hp. However, the power curves will look alot different. The 20lb pulley will make the 500hp much sooner in the rpm range because boost will build much faster and power will not rise at the same liner rate as it would if you ran just the 10lb pulley.
-Corey

Not trying to contradict in any way as I have never had any form of blower or turbo so this is just me thinking out loud. Given the above you would have more peak hp by running a 10lb pulley to get 10lbs of boost vs. running a 20lb pulley and blowing off 10lbs of it. Now that 50 extra hp would look good on paper, but shouldn't the hp and tq picked up lower in the RPM range be worth the 50hp peak to peak trade off? I mean if you lost 50hp at 6500rpm lets say, but at 5000 you gained 20 because you were already at max boost wouldn't it be better on the street and on the track to have max boost sooner?

Originally Posted by INDY

I WOULD NOT ADVICE DOING THIS, its not worth it just do as recommended in the quote. It will reduce the life of your blower, and create a higher average intake air temp.

Well I guess it would depend on the blower and intended use really. For example putting a 20psi pulley on a P1sc and only using 10psi of it, but what if you were to use a D1 instead of a P1?? This system would really be good for guys like us who plan on using the stock block for a little while and have been going with the P1 to keep the boost down. Now they can get the D1, keep the boost low, then when they build a shortblock they can just sell of the blow off valve setup and runn the D1 to its potential.

Also lets say you are running a P1 @ 10psi currently, you use the blow off and pulley the s/c for 15psi but dump the extra 5psi. you would see max boost earlier in the RPM range which would be good for a street car and running the P1sc to 15psi vs 10psi probably wouldn't put too much extra wear on the head unit. I could see if you pullied it for 25psi and only used 10psi but pushing it a bit harder than your intended max boost should not let the extra wear outweigh the earlier boost.

[INDY]

We have done this at the shop with P1s, D1s, vortex, and paxton blowers. And trust me the head unit gets hotter, and your ITA temps raise too because the blower is being spun a lot harder.

Feel free to put a blow off valve on a blower car, but IMHO I wouldn't recommend it.