The Great Boost Discussion Thread - GOOD INFO INSIDE!!!

[NXcoupe]

Re: In Response to Javi's Post....

I wrote a long reply, but then I just deleted it. dogmatacism is great.

 

[wannaboost94gt]

Re: In Response to Javi's Post....

1.Turbo
2.Centrifugal
3.Twin Screw
4.Roots
As far as the 1/4 goes.
Turbos kick ass but are quite a bit more difficult to install. + 1 for the hairdryers!

 

[Hellion94]

Re: In Response to Javi's Post....

1.Turbo
2.Centrifugal
3.Twin Screw
4.Roots
As far as the 1/4 goes.
Turbos kick ass but are quite a bit more difficult to install. + 1 for the hairdryers!

I think that's a little too general. There are several situations in which a Roots or twin screw may outperform a turbo or centrifugal, and vice versa. Again, that will depend on a lot of factors besides the supercharger or turbo itself.

 

[OnyxCobra]

Re: In Response to Javi's Post....

KB is always advertising that their blowers don't have a drop off in boost from 2000rpm to redline, so really why would it taper off?

 

[Hellion94]

Re: In Response to Javi's Post....

KB is always advertising that their blowers don't have a drop off in boost from 2000rpm to redline, so really why would it taper off?

Well, they aren't lying, as the boost may not drop off, but the efficiency will decline. Boost is just a measurement of the amount of air that backs up in the intake tract as the engine rotates, or positive manifold pressure. Boost isn't what makes power. Boost is just the measure of pressure in the intake tract.

This is why a 60mm turbo that generates 20 psi of pressure on a 300 cubic inch engine will make the same, or less power than a 80mm turbo that makes 6 psi on that same engine. It's also why you could put an S-trim on a stock 5.0L and make 10 psi and 350 hp, and then put an H/C/I package on that motor and make 8 psi and 450 hp. Boost isn't what determines the power level, it's the efficiency of the compressor in relation to the engine,or the combination of both.

Basically, any compressor will hit an efficiency wall at some point, and just not be able to make any more power. The way that the positive displacement blowers compress air tends to generate more heat than a compressor that uses an impeller. This just hampers their high-rpm power, as least on the street-sized blowers.

An interesting example of the boost doesn't equal power concept:

When Urist used to run a turbo combination, he had a 91mm that made great power at 24 psi. We thought we'd turn it up at a race (WFC I think) and cranked the controller to 28 psi. The car went 1/10th slower than it had the previous run. Basically, we had found the sweet spot for the compressor, and there just wasn't anything to gain by trying to spin it harder.

 

[Paul]

Re: In Response to Javi's Post....

When you say "we" - do you work for Hellion? Are you a crew member for Urist?

 

[Hellion94]

Re: In Response to Javi's Post....

When you say "we" - do you work for Hellion? Are you a crew member for Urist?

Yeah I worked there for about 3 years, and I still handle a lot of their graphics and marketing. We have been going to races and helping out for about 8 years or so.

 

[95PGTTech]

Re: In Response to Javi's Post....

I love how everyone is debating this like we are building an Outlaw car and looking for those last hundreths of a second and going 200mph+. Compressor maps and discussions of efficiency. LOL. You are so far and away from the original topic and scope it's not even funny.

It's a street car. Any choice is going to make it feel, and be, a whole lot faster than before. Buy whatever one you think looks cool, you can get a deal on, you think would be easier to install, or whatever your local shop sells. Any way you go - centri, turbo, or roots - a new one or a ten year old kit - intercooled or non - you'll be happy.

That's why they're street cars. They're just supposed to be fun and quick.

 

[Paul]

Re: In Response to Javi's Post....

I wouldn't buy a blower/turbo for my streetcar either without a compressor map. There's no reason NOT to match it appropriately to your motor. Understanding and applying the science behind compressors isn't just applicable in Outlaw cars.

Paul.

 

[Hellion94]

Re: In Response to Javi's Post....

I wouldn't buy a blower/turbo for my streetcar either without a compressor map. There's no reason NOT to match it appropriately to your motor. Understanding and applying the science behind compressors isn't just applicable in Outlaw cars.

Paul.

That's really what I had in mind starting this thread, more of a theological discussion of what people thought were best suited to which engines. I agree with you on this completely, If i'm going to make the effort (or spend the money) to add something like forced induction to my car, I want to at least make sure I can get the most out of it.

On the race level, it gets either much, much more in depth than what we are saying here, or much, much more general. Race cars and their builders tend to latch on to and follow trends. It really only takes one guy or one team spending the time researching to develop a perfect combo, and then everyone else just tries their best to duplicate it, at least on the power adder side of things.

 

[95PGTTech]

Re: In Response to Javi's Post....

I wouldn't buy a blower/turbo for my streetcar either without a compressor map. There's no reason NOT to match it appropriately to your motor. Understanding and applying the science behind compressors isn't just applicable in Outlaw cars.

Paul.

But you get what I'm getting at. He's not going to feel the 20hp gain he's going to get between buying a used, generic kit and going through all the effort and expense of getting something custom to his application. It'd be similar to buying a custom Ed Curtis cam and degreeing it in on a car that just has intake/exhaust.

 

[Paul]

Re: In Response to Javi's Post....

I do understand that for your average guy with a an intake manifold and shorty headers, he doesn't need to know how to read a compressor map in order to buy an S-trim and spend an afternoon installing it.

That being said, I'd argue that having a more complete understanding of what is happening under the hood, and why, is always good practice. :grin:

Paul.

 

[modo]

Re: In Response to Javi's Post....

I wouldn't buy a blower/turbo for my streetcar either without a compressor map. There's no reason NOT to match it appropriately to your motor. Understanding and applying the science behind compressors isn't just applicable in Outlaw cars.

Paul.

But you get what I'm getting at. He's not going to feel the 20hp gain he's going to get between buying a used, generic kit and going through all the effort and expense of getting something custom to his application. It'd be similar to buying a custom Ed Curtis cam and degreeing it in on a car that just has intake/exhaust.

you should use a degree wheel on every camshaft you install. that doesn't mean you should advance / retard it but i don't care who's cam it is it SHOULD be checked.

one of these so called cam experts sold me a cam with everything needed. good thing i checked what he sent me. the pushrods were .5" too long. yes half a inch

 

[95PGTTech]

Re: In Response to Javi's Post....

That being said, I'd argue that having a more complete understanding of what is happening under the hood, and why, is always good practice. :grin:

Paul.

Definitely agree.

you should use a degree wheel on every camshaft you install. that doesn't mean you should advance / retard it but i don't care who's cam it is it SHOULD be checked.

A quick search on me here would reveal me preaching this message, among others. You get my point though.

 

[MustangChris]

Re: In Response to Javi's Post....

id like to see more technical information in this thread... we have alot of smart vets in here...

im curious as to the problem with head size. it makes sense that too large of a head will cause problems with velocity... i assume its like having a garden hose without a nozzle on it, and having a garden hoze with a nozzle...

how do we determine the proper head size? should we match the head to the blower, or the blower to the head?

what would pros and cons be of improper matching? eventhough the heads are overkill and the blower is the bottle-neck, would my reliability and MPG be better than a larger/better blower with the heads as the bottle neck?

As 95PGT said, finding a good deal is a selling point to many of us (not me... but some of us)
and Paul has always been a strong proponent of using efficient, yet cost effective equipment.

also, as paul said, "Understanding and applying the science behind compressors isn't just applicable in Outlaw cars."
obviously, if you want a good, reliable car that will last 500,000 miles... you wont just slap on whatever kit you find on craigeslist...

do you guys have any resources that helpped you? (other than a $50,000.00 trade school)
do alot of these same principles apply across the board? (VVT, pushrod, modular, DOHC, SOHC, 3v, 5v, etc?)

 

[95PGTTech]

Re: In Response to Javi's Post....

im curious as to the problem with head size. it makes sense that too large of a head will cause problems with velocity... i assume its like having a garden hose without a nozzle on it, and having a garden hoze with a nozzle...

how do we determine the proper head size? should we match the head to the blower, or the blower to the head?

each to each. it's not only head to blower. its head to cam to displacement to rod ratio to rpm to intake to exhaust to fuel system to supercharger displacement to boost level to.........it's an entire package. sit down, decide what you want out of the car, and form a plan from the start to get the most effective results. putting a ton of effort into deciding what turbocharger is best for you and then changing your setup throws that effort out the window.

what would pros and cons be of improper matching? eventhough the heads are overkill and the blower is the bottle-neck, would my reliability and MPG be better than a larger/better blower with the heads as the bottle neck?

using turbos as an example - too big turbo could result in late spool. too small could be choking the top end, putting a lot of IAT heat in the motor, short powerband. personally, I am a fan of (street cars) just basic rod/piston setups and leaving everything else stock and doing turbo setups. I'll take a slightly larger turbo than recommended. keep my nice idle, good driveability characteristics, and make my power on boost and tuning. mpg stays decent with the large turbo mostly staying out of boost unless I WOT. but again, this is personal preference. some people like a nasty cam and a clanky motor to feel tough.

do alot of these same principles apply across the board? (VVT, pushrod, modular, DOHC, SOHC, 3v, 5v, etc?)

it would apply to any air pump


there is absolutely no reason why the normal off the shelf used stuff you see on craigslist wouldn't last 500,000 miles. unless you are buying low quality parts, that is another issue. but buying a s-trim kit versus a t-trim kit for your setup is not going to get you any more or any less reliability out of it. what we are discussing is what will be most effective for a setup...I can buy this ***INSERT BRAND NAME*** GT3576R turbo kit for $4900 from vendor X or there is an option to upgrade from the .82 A/R to the 1.02 A/R for $200. Is it worth it? Is it going to spool correctly and flow enough up top for my setup? Should I go with the V-band housing for another $200? How about the twin scroll or the anti-lag inlet?

 

[MustangChris]

Re: In Response to Javi's Post....

when sitting down for a build, where do you start? (personally, i have a feeling thats a pretty personal question)

 

[95PGTTech]

Re: In Response to Javi's Post....

when sitting down for a build, where do you start? (personally, i have a feeling thats a pretty personal question)

yes.

I start with my goals.

my first question to a customer is what do you want to do with this car? daily driver, weekend cruiser, weekend warrior, or full race. the first two never see a track. a weekend warrior is a mix. if weekend warrior or full race, what type of racing (drag, autocross, road course). we then determine a class, if it's a class racer. class racers are relatively easy to build, as they have a set of maximums already as to how you can build a car. if there is no class and just a generic time trials car or HPDE car or bracket racer or whatever it is a bit more flexible.

budget is usually the next consideration. personally, I then start with motor and trans as they are the most expensive and time consuming parts usually.

 

[Hellion94]

Re: In Response to Javi's Post....

I agree with everything stated.

The best way to go about starting a buildup is to assess your goals and budget, and see which parts and pieces in the combination can get you the best gains for your budget, i.e. don't buy a Dart Iron Eagle block when all you have is a $2,500 budget for a street setup. Spend that money on a good HCI combo, or whatever will get you closest to your goal.

 

[Dalamar]

Re: In Response to Javi's Post....

definatley good advice.