jpc350z

This thread has gone all over the map.. The question that was raised is how much engine power does it take to drive a S/C? (which in turn produces additional engine power)? Parasitic loss..Example: If you had a S/C car that develops 400 hp at the wheels what would be the power bhp output of this engine if the S/C took 0 engine power to operate? (Drive train losses would be the same with or without a S/C).

Confusing the issue with comparisons to other F.I. sytems or efficiency's of different systems while interesting and also debatable only confuses what is a rather simple question.

booger

iTrader: (6)

Exactly...seems its hard to stay on topic here .

http://en.wikipedia.org/wiki/Supercharger
Here is a link that gives some info on parasitic loss . Scroll down to the part that talks about Rolls Royce aircraft motor . The motor makes 750 N/A and the SC adds 250HP but takes 150hp to turn it .

I dont think the amount of power to turn a SC would change from motor to motor that much . But you would think it would be much easier to make 250hp more on a huge motor like that , than the 200whp + I've added to my motor .

sentry65

iTrader: (11)

I know I shouldn't post because I'm supposivly polluting the thread but...

that's an airplane engine put in planes that fly up to 24,000 ft above sea level
http://en.wikipedia.org/wiki/Rolls_Royce_Merlin

I honestly wouldn't expect it to perform like it would close to sea level, so of course it's going to have a harder time making positive power at high altitudes - why modern high altitude planes use turbos


interesting that this was posted here: http://en.wikipedia.org/wiki/Supercharger
sounds like it's making power just fine at lower levels - just happens the engine wasn't strong enough to handle it at low altitudes

booger

iTrader: (6)

SO how would you think they knew the power out put of the motor N/A , and then SC'ed ? Do they have a huge engine dyno in the sky ? That flies around with the plane ?

Give it a break please ! You know all I was doing was trying show how much power it DOES TAKE to turn the blower . That big of a motor will produce 250hp more alot easier than our motor will produce 200whp . And it still takes 150hp to turn out 250hp more at the motor

The evidence against your side of the arguement is adding up .
So please stop trying to split every hair you can , to keep your self from thinking about the truth .
If you want to continue the arguement...START YOUR OWN THREAD PLAESE !!!!!

sentry65

iTrader: (11)

booger, what evidence?
I'm not a pro tuner or shop owner, but how many pro tuners or shop owners are qualified to calculate parasitic loss? Not all, but many tuners are more concerned with putting parts on a car to make it fast and then tuning the A/F, timing, and boost. Chances are they can only guess what they think the parasitic loss is on a SC. If THAT'S your "evidence" then ok you win. However I am really interested what their reasoning is and how they'd arrive at their guess though - hence this whole discussion being in order

So far we have the Dsport article that says a SC takes more fuel to supply a given wheel hp level and that difference can be considered parasitic loss.

Sharif said he agrees with that
I said I agree with that...because there IS parasitic loss


so far your whole arguement otherwise has been that because your belt is slipping at 13 psi no matter how tight you tighten it with the CRAPPY stock vortech belt setup that you've reached the event horizen and the parasitic loss ownz youz

Just because your belt is slipping doesn't mean the "parasitic loss is suddenly out of control". It means your belt is slipping and maybe you should get that COG setup on so it doesn't slip. If you end up making 15psi AND making more power, then you know you're still in the good and your vortech setup isn't a lost cause or whatever. Otherwise, why in God's name did you buy that COG setup if the parasitic loss is so huge that it would outweigh any power gain?


So far plumpzz (who's an engineer major) and I came to the table with the math formulas that engineers rely on for these sorts of things and you dismissed it since it's over your head. the numbers we came up with were roughly a 1/3 of what you claim



I can start my own thread but it'd be redundant.
BTW you DID call out my name in THE 1st WORD OF THIS THREAD.
Because of that, I should have the right to post in your thread

if you don't want a discussion, then you should have started a poll



again, if my vortech is taking 100whp to turn the blower, then I'm right up there with breaking the record for the most power the stock block can handle on the engine itself cause that'd mean my engine is taking 560-570whp worth of abuse to output an actual 460-470whp. And all I gotta said is DAMN these engines are strong and/or DAMN my car must be set up to be safer than anyone else's stock block/high power engine to date....and I just don't think either is the case


I'm going to guess that they used good old fashioned engineering to calculate the power based on the boost and altitude. I could be wrong, but I'd think they were mostly concerned with how the engine would perform in its working environment. They did say at sea level the SC would make so much boost it would damage the engine, so what good is that?

Oleg

iTrader: (1)

There was sometthing about the blower on the top fuel drgasters consuming like almost a 1000hp...

Sharif@Forged

iTrader: (92)

For what its worth, I have a fair amount of experience "trying" to tune high boost ATI kits. From what I have seen..after about 11psi, the air inlet temps go sky high...over 140F, and there is no more power to be had even with 14-15psi boost pressure. We gave up on trying to make 500whp+ out of the SC kits...not sure if Vortech would be the same. Sam at GTM struggled to get to 500whp with the Vortech.

Maybe these is the reason, there "appears" to be more losses at higher boost pressures??

sentry65

iTrader: (11)

Sharif I'm curious, since the intake temps are so much higher than normal as you approached higher power, do you think that would be an indication of either the intercooler isn't sufficient and/or the blower is running out of efficiency? Were any of these cars running water injection? That's supposed to lower intake temps 20-40 degrees from what I've seen

I'm trying to understand if it's even possible if mechanical parasitic loss can increase air intake temps

booger

iTrader: (6)

My god !
First...and this will be the last . What the hell does belt slipping have anything at all to do with parasitic loss to turn a blower ? 0 - none-
ziltch . I used it as an example to show that it [ the blower ] is harder to turn as PSI rises . AND that means the parasitic loss increases as the psi rises .

Second...Your math figures are just that . And doesnt take into consideration the power it takes to turn the blower increases as the rpm's and power goes up . Your figures are to turn the blower only . Not to turn the blower at the upper rpm band . And thats where most of the power [ parasitic loss ] is .

Third ...what have you come up with other than a math calculation to figure out what I stated above .

fourth...If you had read the link I posted . You would also have noticed , in a two speed SC [ in a airplane ] that it took 400hp to turn the blower .

fifth...The DSport mag article , and the article in the link I posted . Sharif agreeing with the artcle , and the guys Ive talked to that have had hands on knowledge of the loss . All leads to the fact that the power loss is much larger than you suggest . We all know we cant pinpoint exact numbers .

sixth...Im just a stupid old man and it doesnt take to much for me to figure this out and come up with a logical decision on the subject . So why can't an intelligent person like your self figure it out .

seven...I asked owners and tuners to give thier opinion .I didnt think they had done testing to figure it out , nor care to . I had no problem with you posting good info on your side of the arguement . But instead you decided to argue about every thing BUT parasitic loss of a SC . WHY ? ..because you dont have an arguement against it . You just like to argue and you like to side step , avoid , and do what ever you can to keep an agruement going with out talking about the subject .

JUST LIKE YOU KEEP DOING OVER AND OVER AGAIN !!!!

RudeG_v2.0

iTrader: (1)

Sharif@Forged

iTrader: (92)

The parasitic losses arent increasing with higher boost, but the blower/intercooler package is probably running out of efficiency..causing the higher inlet temps. My point, is that this can give the illusion of greater parasitic losses, but it might just be hot inlet temps as the culprit.

Havent tried meth on the SC.

booger

iTrader: (6)

So you are saying . It takes just as much HP to turn the blower at idle as it does at higher rpm and boost ?

You second part of your statement...that its probably the blower / intercooler package running out of its efficiency and hotter temps that make it look like higher parasitic loss .

Ok...let see if I can state this right .
We did log intake air temps before the W/M injection , but I dont recall what they were . I do recall my shop saying they werent high at all for the psi I was running [ new bigger IC and IC pipes ] . The W/M injection did lower the temps quite a bit . So efficiency shouldnt be a problem that makes you think its NOT parasitic loss .
So I have belt slipage at the same psi before the bigger IC and IC pipes . It was just happening at different rpm level [5900 instead of 6300rpms ] . This leads me to believe that at some certain point [ 13psi ] the blower has gotten harder to turn . Hard enough to turn as the serp belt will no longer hold and starts to slip . Think of it this way , there is a restriction between the motor and the blower [ the IC ] and even the motor its self is a restriction . The blower is pushing air thru the IC and at some point the IC slows up the air flow and boost begins to build . The air will only go thru the IC so fast and not as fast as the blower will produce it . So the restriction [ the IC and motor ] is making the SC work harder to produce more boost as rpms rise . The SC working harder means its getting harder and harder to turn . Parasitic loss is going up and up with the SC working harder and harder . And [ for my set up ] at 13psi the SC is hard enough to turn , that the serp belt no longer holds . It slips , the SCer's rpms drop slightly and it isnt as hard to turn and the belt grabs again .Over and over , slip grab , slip grab . I just cant believe a SC takes no more hp to turn at idle than it does when its making 8-9-10-13psi . It has to rob more power from the motor as boost rises . The motor has to be working harder to turn that blower .

Sharif@Forged

iTrader: (92)

Part of the reason we gave up on high boost SC, is due to premature belt snappage, and slippage.

I am not a parasitic loss expert, nor do I claim to be. But what I have observed, (with an air inlet probe just prior to the TB), is air inlet temps that were about 70 degrees over ambient...thats pretty hot.

An SC takes engery to spin....as do turbochargers. I think we can all agree on that. The 350Z SC kits take more engery to spin, when compared to a turbo charger..hence the higher parasitic looses. Turbochargers get a discounted lunch, but not a free lunch.

As a percentage basis, I dont see how the SC would produce lower parasitic losses at idle...vs. redline. The % should be identical, but of course, the absolute parasitic loss would much greater at higher RPM and power levels.

I didnt read all of your posts closely...both Booger and Sentry, so forgive me if I missed your reasoning.

sentry65

iTrader: (11)

parasitic loss does increase as the power rises....I agree with that because you're making the blower spin faster and that takes more effort than spinning the blower slower. That also runs inline with all the math equations I've seen on the subject




yes they did, they factored in a given psi number, a given rpm, and a given CFM (airflow)

and what have you come up with other than repeatedly saying the parasitic loss increases as boost goes up and that it's something like 100whp of drain? (which you're just guessing at- I assume you mean yours and my power levels)

booger, that article is just saying that there's parasitic loss and that can be accounted for due to the extra fuel SC's use. The severety of the mechanical parasitic loss on different setups with different cars to my knowledge was never brought up.


his agreement if I understood how he wrote his post means he agrees that the difference in fuel between NT/turbo and SC can be considered a measure for parasitic loss. The way I took it was he didn't really "side" with anyone in regards to how severe the parasitic loss is at different power levels on a Z/G

all your buddies prove is that on their setup they wanted more power. If they couldn't get the belt to grip, than that's a grip issue. If your buddies needed a larger FI adder than what their SC was and they're shooting for the moon, then why not go turbo? Dsport with the cog pulley vortech setup was able to grip just fine up to 19 psi or something??? His problem was trying to rev to 8000 rpms and snapping the belts. Who's to say parastic loss snapped his belts and not just stress?




and you'd also notice that it says:
seems inline with a regular SC parasitic loss to positive power trade off to me...how's that out of the ordinary? It's just a larger scale of power

sentry65

iTrader: (11)

I didn't think the intercooler actually slows the air down in quite that way - I mean, it is a restriction, but I thought too small of an intercooler would actually speed the air up and thus heat it up more because of both higher friction and less time being intercooled. To my knowledge, the first real restriction to slow the air down is in the intake mantifold and the engine itself with the valves opening and closing

the blower is easier to turn if the pressure itself was lower but overall the car was making the same power due to a really large exhaust?

For example, which do people think is harder to turn the blower at?

470whp @ 12 psi
or
470whp @ 14 psi

the higher pressure in the manifold means the air is harder to compress and so earlier in the line the blower isn't able to spin as freely
This is why I think a stroker kit and bumping displacement, thus lowering boost will let the blower still spin easy and not slip the belt as much as a higher manifold pressure

IMO I'd rather have more flow than more pressure

booger

iTrader: (6)

Not trying to argue about the ATI SC you worked on [ Treflings car ] But if I recall right . You guys were trying to run with out a IC at all and just do W/M injection . So Im sure intake temp were high and the W/M couldnt bring them down enough . The combination of a bigger IC , IC pipes, and W/M injection is going to bring the intake temps down quite a bit . Besides the fact , turbo cars have the same problem [ cooling intake temps ] SO why would it only be a problem with a SC ?
Sentry is saying that it takes a mere 25whp [ not sure on exactly what he stated ] to turn the blower at the upper rpm and boost levels . Im stating its taking much more than that . I had stated it COULD be taking up to 100whp at upper rpm and boost levels . I have to think at 420whp [ his and my whp level ] thats it got to be much more closer to 100whp than 25whp to turn the blower . I can except that it doesnt take any more % of power from the motor . But the number itself is going to go up

sentry65

iTrader: (11)

as long as the engine is happy and making the expected power it should, i'm happy whatever the parasitic loss is

At the end of the day, the parasitic loss could be 1000whp and as long as the engine holds and can take a beating, I suppose I don't really care what the actual number is.


this has been an interesting debate


I remember Trefling's experiment without the intercooler - that was an interesting test and I do think it'd work out ok for really low boost like 4-5 psi maybe?
https://my350z.com/forum/forced-induction/183366-no-intercooler-with-water-injection.html

booger

iTrader: (6)

Ok ..so now basicly you are agreeing with me now ? . This whole time you have done nothing but try to agrue against my point on the blower being harder to turn as rpm and boost rises . But complicating the matter by adding in a new spin on it just takes the subject off topic .

Quamen

iTrader: (14)

It was mentioned that Top Fuel dragsters have used 1000hp to turn the blower but that is not comparing apples to apples. Those are positive displacement blowers which do require a larger amount of power to turn than centrifigal and have a higher internal compression ratio.

sentry65

iTrader: (11)

no booger I've been holding the same stance the whole time. In fact I've been agreeing with you about as psi rises, the parasitic loss increases. I can find several quotes in this thread of me saying it, but it shouldn't be necessary.

IMO I wouldn't want more than 12 psi in the manifold. Once I'd want to go beyond "12 psi" or my current power numbers, I'd probably go with a stroker kit to drop the pressure down. If I wanted to raise the boost pressure back up to around 12 psi, then i'd need to switch to a T-trim blower and that's about as far as it can be taken IMO


BTW, this sorta parasitic loss we've been talking about in the last few posts occurs on both SC and turbos. The issue seems to be the longer belt having a harder time gripping the SC pulley at the higher pressure numbers.

The parasitic loss I thought we were really talking about was the mechanical parasitic loss, or the act of a larger belt having to turn a blower. What I've been disagreeing with you about in regards to parasitic losses is how severe they are. You're using your belt slipping at 13 psi as an example to show the blower is harder to spin faster as boost rises, that's fine and I'm ok with that. I also think part of the reason the belt is slipping is the bad belt design, which you obviously acknowledge because you bought the Cog setup I'm guessing because you think it's a superior design. At the end of the day, the parasitic loss doesn't matter if you make power

I do think it's possible to make well over 500whp from a Z/G in one form or another with a SC and VQ engine, but it isn't going to involve spinning a blower to insane speeds reaching excessive high amounts of pressure in the manifold and engine. I don't think reving to 8000 rpms (which obviously spins the blower faster) is a good path to take nor do I think putting on a T-trim blower in combination with smaller pulleys to create lots and lots of boost pressure is the way to get significantly more than 500whp. I think a stroker kit and headwork are going to be key issues for better power...IMO

The 6 liter LS2 engine reaches 600hp with only 6 psi with a procharger....I think that's a successful model to follow: larger displacement + low pressure + decent efficiency = decently large power. I think switching to larger displacement gives you a new lease on making more power since it will lower the manifold pressure and naturally be able to accept more air more easily. What you want is increased air flow volume, not increased pressure. Increased pressure can possibly cause damage


If I was shooting for the moon with power and was going to do it with a 3.5-4.2 liter engine, the only way to get more power is to increase the boost pressure coming from the FI kit. So switching to a turbo would probably be needed because I really do think the belt slipping issue is going to get out of hand beyond 12 psi.

Dsport drove that T-trim to 19 psi and that air was probably fairly heated up and the compressor efficiency was probably in worse shape having to be spun so fast at 7400 rpms that he "only" achieved 510whp or so...at 19psi
I think he was running into a wall of parasitic loss and compressor efficiency, and possibly intercooler limitations right around there, but you and me don't rev to 7400 rpms and we don't overdrive the blower as much as he was