parish8

iTrader: (6)

I am not seeing 1000whp at 17psi. The 1000whp run is labeled 22psi and does not say the blower is there.

smokeshow

iTrader: (17)

^ The devil is in the details lol. As is obvious by the 89hp gain (12% increase) with the turbos only in that Hellion video, you don't really get the best of both worlds. You get a compromise, at best. You can do as I did and open the blower bypass once the turbo hits a preset boost level. This is a TVS 1900 and S475, sequential boost:









It worked really well I'd never run a traditional compound on a gas engine. This method of a blower/turbo combo will do everything you need and more.

WstSidHomE

http://www.yellowbullet.com/forum/sh...light=compound

This thread has a huge amount of information. You have to weed out the misinformation that some people throw in though. A few of the guys in this thread have compound turbo setups with pictures and lot of details and results from different turbos on their setups. It's a really good read, but it'll take a while to read it all! lol

parish8

iTrader: (6)

long is ok. the more info the better. thanks.

parish8

iTrader: (6)

that video is missing too much info to draw any conclusions from. a big part of this thread is the argument that you need to run very large turbos if you want the high efficiency that you would normally see from turbos only. a pair of 61's appears to be way too small.

from what i am learning from this thread and the links on this thread the way you did it does not appear to be the only way to go or even the best way to go.

i question the compromise aspect of the compound set up. i think with a proper set up it really can be the best of both worlds and maybe even better than both worlds in some ways.

WstSidHomE

no problem. anything to help, i love seeing and hearing about people willing to try this on new foundations.

smokeshow

iTrader: (17)

The video had enough information to show the power loss from running the blower in the mix lol... One simple modification and the power is gained right back. What you gain in cleaning up the air charge with the PD blower, you lose from the parasitic loss of the blower. The comparison isn't even close.

RonA

iTrader: (1)

A better way to run those tubos would be to set the gate on the secondary so that it starts to open at about15psi. Run the primary turbo up around 35 to 45psi, and let the secondary run at the lowest pr you can and still move the air from the primary into the motor. For more torque, run the secondary a bit harder.
As hard as this little MP112 pulls on the bottom end, I think a 88 or 90mm primary would come up on boost hard by 3000rpm and move double the air mass into the supercharger by the time you got to 4000-4500rpm. You'd have major torque from the supercharger at low rpm, and twice the air mass on top. With good cylinder heads, it seems like a win win.

parish8

iTrader: (6)

yes i can see that top end power was gained when the blower was pulled off, graphing boost would add a lot to the value of this test. what you continue to ignore is that they are using too small of turbos to work ideally with the compound set up. i contend that with proper sized turbos the top end loss would be limited to only what the belt draws and might be made up by having a exhaust/intake pressure ratio of less than one. there is a ton of good info in that link above.

let me do the math on that gt500 set up and try and explain it to you for this particular set up.

stock boost on a gt500 appears to be around 9psi. looking at the chart above that means the turbos will need to be sprung at only 5psi. (5/14.7)+1= 1.34 pressure ratio is all those turbos will be at to make 17psi total.

next part is airflow. just a guess but for 700rwhp i would say 40+lbs of air each. now look where on the compressor map you land at 1.34 pressure ratio and 40+lbs of air with a 61mm turbo.



compare that to a pair of large turbos where the turbine will be much larger(less back pressure) and the eff of the compressor will be much higher(less heat) and things are likely to improve.

the point is whatever turbos are going to work great without the blower are going to be too small with the blower even if your max hp goal does not change. i do not know how much real world effect there will be between running your turbos at 60% eff compared to 78% eff and how much a larger turbine housing is going to do. i suppose the next logical step to do if we are playing with the numbers is calculate the temp difference and what that would do to the hp. that would account for the eff loss of the too small turbo but not the reduced back pressure.

edit: i just did the math on just the added heat. i am not 100% sure on the math that i did but what i came up with when comparing a 55% eff comp for just the turbo compared to putting a turbo that is at 78% you gain about 30deg in temp and loose about 30hp. if that is the case then the hp diff at the very top shifts from 800vs711 to 800vs741. now lower the back pressure a little and likely gain more. once again without over laying the boost on those 2 runs we are just guessing.

smokeshow

iTrader: (17)

I know the math, Jim. And I agree with what you're saying...the blower+engine combo looks like a much bigger engine to those turbos, which are too small, as you said. But negating all the detains in this specific application, a turbo is still a far more efficient use of energy. The return from a blower is unarguably lower than that from a turbo. So it makes sense to use the blower to give you what you want (instant throttle response) and let the turbos take over once the blower has done its job. I posit that, given a setup that is optimized for a turbo, the engine will make more power and have a much lower BSFC with the blower running sequentially rather than compounded. This stands regardless of the turbo size, either running these turbos in the hellion kit, or larger ones... The net effect of not running in compound will be the same: more usable power.

camarokid94

iTrader: (2)

soooo what did we decide here??????????? I have a customer with a 2300 maggy on his 6.2 ls3 that we were going to do a twin turbo build on and now hes asking if we can keep the blower and just add the turbos so its still got gangster low end instant TQ but more HP up top...? its a street car not a drag car and built more to have fun around town than anything soooo??

Atomic

iTrader: (37)

I talked to a couple guys that have done this back in the 80s and 90s and a problem they kept running into was eating the thrust bearings on the roots blowers. Something to keep in mind anyway.

As far as sizing, size the turbos for the CFM of the blower, not the engine. So if its a 6.2L and runs a 7lb pulley on the blower, size the turbos for a [6.2*(7+14.7)/14.7))=9.15L engine.

parish8

iTrader: (6)

which in my mind would be a pair of 76's.

i hope to do this some day. 6.2 lsa with the stock blower and stock pulleys and a pair of 76's. if i ever decide to ditch the blower the 76's would be easy to sell.

camarokid94

iTrader: (2)

well hurry up and test this theory out so the rest (me) of us can see if should follow suit!!!!

chuntington101

I still think it comes down to what you are trying to achieve. If you are drag racing a car why the hell do you give a **** about the low end response of the engine? All you need to focus on is power around and above the stall point and maximizing that.

For road race you are probably only talking about 50% of the RPM range. If you are at any lower RPM than that and your in the wrong gear.

So once again what are you trying to achieve? For gut wrenching bottom end why not just push 20psi through a SC alone? if you want massive peak power than you aren't worried about the bottom end so ditch the SC and let the turbos do there work. Plus you can then use a decent intake manifold and get the advantages from that.

For a street car, Just match the turbos to the power you want to make in the RPM range you want to make! Simples.

I have seen 1.3ltr motorbike engines pushing 500bhp with little to no lag when used in a road race style car (Dax kit car). The turbo was a ex 1980s F1 unit and not using the latest technology (a Garrett TR30R would be even better!) and still response was great because the turbo matched the characteristics of the engine and what the person wanted to achieve.

Chris.

ls1_chevelle

iTrader: (9)

If you decide to ditch the blower, Id rock the 76s on the LSA! lol

parish8

iTrader: (6)

i really dont disagree with anything you said and i would not pay for both a blower and turbo.

i am more interested in if i all ready have a blower because it came on the car what are the advantages and disadvantages of keeping it or removing it when adding turbos.

i am hoping that using both will allow the car to rip off the line with a stock converter AND make obscene top end power while driving like stock.

chuntington101

From a technical level i love the idea of getting both the blower and the turbo(s) to work together and get the best of both worlds. However, having discussed with some MUCH smarter people than me, i appreciate the complexity of something like compounding and how effective well designed turbo systems can be these days!

stage274

I am sorry, but I think it's gay to do this. The only compounding one should do, if you have a blower car, is add nitrous. Lots of it, if you are not makeing the power you want. Which will also cool the blower charge. Blower and nitrous is a pair made in heaven. And this is a way to approach turbo efficacy and turbo torque with a blower car.

If you have turbos, a small shot would help off the line, like a 50 shot. I am not a fan of using nitrous on a turbo car though. Because you can leave fully boosted. But I can see how lag would effect roll races. If that is your worry, a 50 shot would help before the coolers.

I am sorry, but it is just gay to me, and a waste of money, even if you got it to work well. Gay...

NateLS1Mustang

iTrader: (2)

Commenting on a thread with a ghey comment two years later is ghey.