Building for torque over HP....
moving on.
RobevoRS: The restrictor is a large part of what helps rally cars make so much torque, but I also thought it was mostly attributed to their Anti-lag systems which spool up a larger than usual turbocharger low in the RPM band.
If the restrictor really helps that much, why don't turbo cars just artificially restrict the charge until higher RPM where it's opened up..... Similar to intake manifold runners which cross-over to highrpm? Wouldn't that provide capability for much more torque without choking the top end? It just doesn't seem that easy, there has to be more to the equation....
Regarding the buy a V8 comment, I still don't see those making 400wtq before 3000rpm unless turbocharged. As I said before I'm not really "serious" just curious. V8's are off topic.
After seeing what people have done on the stock turbo I'm thinking this goal can't be too far off.... Full-bolt on Stock-turbo Evo 9's have made 400wtq by 3000rpm which is incredible.... Considering Evo X has better spool potential, you'd think a built motor could spool a slightly larger turbo about as fast to make more than 400wtq.... The way I see it spool is really what matters. It's just that the stock motor will puke it's guts out if you spool it up any faster.... built motor won't, yet no one seems to attempt to quick-spool one.
Again I'm just curious and looking to chat about this type of build. I'm not trying to do this on my car. I like the theory behind it.
If the restrictor really helps that much, why don't turbo cars just artificially restrict the charge until higher RPM where it's opened up..... Similar to intake manifold runners which cross-over to highrpm? Wouldn't that provide capability for much more torque without choking the top end? It just doesn't seem that easy, there has to be more to the equation....
Regarding the buy a V8 comment, I still don't see those making 400wtq before 3000rpm unless turbocharged. As I said before I'm not really "serious" just curious. V8's are off topic.
After seeing what people have done on the stock turbo I'm thinking this goal can't be too far off.... Full-bolt on Stock-turbo Evo 9's have made 400wtq by 3000rpm which is incredible.... Considering Evo X has better spool potential, you'd think a built motor could spool a slightly larger turbo about as fast to make more than 400wtq.... The way I see it spool is really what matters. It's just that the stock motor will puke it's guts out if you spool it up any faster.... built motor won't, yet no one seems to attempt to quick-spool one.
Again I'm just curious and looking to chat about this type of build. I'm not trying to do this on my car. I like the theory behind it.
Sure you make a big pipe smaller with a restrictor.... but suddenly the same air has more velocity. More velocity means with the same amount of "valve-open-time" you get more air.
If I setup an ActionFigure on the table I can blow through a straw and knock it over. If I breathe through a paper towel roll, I cannot knock it over unless I'm right next to it..... With the straw I can be farther away and still get enough air velocity to knock over the action figure.... So this issue is not just flow but also velocity.
I believe that has to do with the restrictor discussion. My guess is it speeds up the slower moving charges. Then eventually it restricts the air just like breathing through a straw does.....
But if you could somehow remove the restrictor as soon as it truly becomes a restriction, you could technically use it to boost the low end response right? (Basically blow through the straw, until it would restrict the air, then switch to the paper towel roll for pure flow.)
Last edited by acidtonic; Jun 12, 2013 at 11:12 AM.
I don't understand it, either, but here's what I've extracted so far: (1) turbos don't produce boost, they produce pressure ratios; (2) turbos are most efficient when prodcuing a certain pressure ratio; (3) if the inlet side of the turbo is in vacuum, due to the restrictor, then the turbo will be at the desired pressure ratio at a much lower flow rate; (4) this much lower flow-rate can match the flow needed for low RPMs.
I have no idea if the above is correct. It's cobbled together from a mixture of web-sites, books, and old-fashioned fill-in-the-gaps-with-stuff-extracted-from-a-dark-and-damp-place. If you don't want guesses, ignore me.
I have no idea if the above is correct. It's cobbled together from a mixture of web-sites, books, and old-fashioned fill-in-the-gaps-with-stuff-extracted-from-a-dark-and-damp-place. If you don't want guesses, ignore me.
Besides being similar to the very first post, how does making an engine that can rev-up faster help all that much with low-RPM torque? The question was how to get power down low, not how to get the engine to a higher RMP quicker. Or am I missing something deeper here?
I don't understand it, either, but here's what I've extracted so far: (1) turbos don't produce boost, they produce pressure ratios; (2) turbos are most efficient when prodcuing a certain pressure ratio; (3) if the inlet side of the turbo is in vacuum, due to the restrictor, then the turbo will be at the desired pressure ratio at a much lower flow rate; (4) this much lower flow-rate can match the flow needed for low RPMs.
I have no idea if the above is correct. It's cobbled together from a mixture of web-sites, books, and old-fashioned fill-in-the-gaps-with-stuff-extracted-from-a-dark-and-damp-place. If you don't want guesses, ignore me.
I have no idea if the above is correct. It's cobbled together from a mixture of web-sites, books, and old-fashioned fill-in-the-gaps-with-stuff-extracted-from-a-dark-and-damp-place. If you don't want guesses, ignore me.
That's exactly the kind of dark-corner-info that I'm trying to expose and discuss. Very interesting!
I'm really interested mostly in tricks to achieve more power sooner.... But I do see the value of spending less time in the lower RPM. It was worth mentioning
Now what about cams and valves.... Do we want huge valves with low lift, or stock-sized valves with more lift? Surely one or the other will help more with low RPM response?
I'm also curious how much more low-end could be achieved by perhaps cheating with Nitrous... On a built motor I'd assume you could essentially spray right from idle? I know on a stock motor you don't spray down low or it will toss a rod. Perhaps a slightly larger turbocharger and a 50-100 shot from idle on a built motor would work??
Is it possible to spray nitrous at the same time as meth/water injection to even further raise timing right off the line?
(Man these ideas do sound crazy, I will admit..... But I'm quite interested in what we could do to push the limits even farther)
Yes, you can definitely optimize the intake plenum, runners, and valves for low-RPM torque. But, because of the no-free-lunch rule, this will hurt the top end.
edit: to be clear, this is rarely worth it on forced-induction
edit: to be clear, this is rarely worth it on forced-induction
Last edited by Iowa999; Jun 13, 2013 at 12:40 PM.
I have a bone stock EvoX turbo. . The usual rally engine if they change anything, they make it only a ball barring turbo(on evos) or they play around materials. Turbo in a rally cars usually stock size. Restrictor plate is there to limit the hp around 300 hp, that is all.
Als is there to keep the turbo spooling when you off throttle, so at least produces a minimal vacuum or above all away to 1.8 bar at idle. It is all driver preferences, i dont like the push takes too much toll on the brakes. I am running 0 psi ALS set up. If this is help to understand the tq -hp-ALS thingy.
Als is there to keep the turbo spooling when you off throttle, so at least produces a minimal vacuum or above all away to 1.8 bar at idle. It is all driver preferences, i dont like the push takes too much toll on the brakes. I am running 0 psi ALS set up. If this is help to understand the tq -hp-ALS thingy.
Last edited by Robevo RS; Jun 13, 2013 at 02:36 PM.
.... Unless you run a super small pulley the supercharger won't really be boosting much down low. If you run a small enough pulley to equal real boost before 3000rpm, it would be so small you'd overboost/overspin the blower above that rpm.
Keep up the interesting discussion
The car you described that was twin charged using a MB supercharger and a large turbo used a positive displacement supercharger. The SC took care of the low end and allowed the exhaust gasses to build up turbo boost until the mechanical clutch disengaged the SC and let the turbo go wild. I believe that the car was featured in DSport.
I'm assuming that you are thinking of a centrifigual supercharger (that builds boost as the rpms build) rather than a positive displacement supercharger (that supplies close to full boost at any rpm)?
The car you described that was twin charged using a MB supercharger and a large turbo used a positive displacement supercharger. The SC took care of the low end and allowed the exhaust gasses to build up turbo boost until the mechanical clutch disengaged the SC and let the turbo go wild. I believe that the car was featured in DSport.
The car you described that was twin charged using a MB supercharger and a large turbo used a positive displacement supercharger. The SC took care of the low end and allowed the exhaust gasses to build up turbo boost until the mechanical clutch disengaged the SC and let the turbo go wild. I believe that the car was featured in DSport.
Another curiosity is a bigger turbo with variable vanes..... Normally only found on diesels due to their cooler exhaust temps. I've heard of DSM guys running these with various forms of success in twin-scroll configuration. Most cannot control the vane actuation and end up finding a happy medium, others fab up control boards to do the PWM switchover.
Compound turbochargers have also been interesting..... This thread a few years ago caught my attention. http://www.dsmtuners.com/forums/cust...bo-set-up.html I wonder what that setup could do on a faster spooling 4b11t?
Also you can havet 3 modes of ALS (All different boost level /aggressive)
Tarmac
Gravel
Snow
Familiar?
PS: the boost what the ALS producing is usually the driver choice, and the tuner sets it for him. I like 0psi what the ALS produces. Which makes the car neutral there is no push , when you off the throttle. Great for the brake life , so doesnt over heats the brakes.
Last edited by Robevo RS; Jun 13, 2013 at 07:52 PM.
most of the post was sarcasm... but my point was the 2.4 and less rotating mass would help the engine spin easier which would create torque easier and sooner not? or is it the other way around?