Jedi54

iTrader: (7)

Dear Mysql,

I like Mysql101 better. That is all.


Regards,
Jedi


I felt I should follow the proper format if I was going to post in here.

mysql

101 has just about 3x more posts than mysql..

staticlag

Note how this is how it should have read:

"Please don't post stuff that vague, because people have the habit of posting on my videos asking why turbos can't rev to 9000 rpm."

staticlag

Turbos on the renesis don't make peak power at 9K because of the side port design. When the engine is turning that fast the exhaust can't exit fast enough because of the restriction. When it can't completely exit then you have some leftover exhaust in the engine for the next cycle, this takes up room for fresh fuel and air mixture. This problem is inherent to the engine and cannot be fixed without some crazy port work.

This exhaust gas buildup contributes to the overheating & seal failures we see on FI engines.

SlideWayz

& for my last post to this thread, I did indeed attack incorrect statements for the benefit of the original post-er.

The exhaust gas issue does constrain things, but given that 9k on the tach is actually 8500rpms, not too much!

That I became frustrated at Brettus' unwillingness to consider the proof (e.g. yes, a Renesis can make peak horsepower close to 9k rpms with a turbo that isn't laggy down low) was admittedly ungracious and unbecoming. Further, since I have two small children I should have learned more patience by now.

So, for the benefit of anyone who actually cares about the original question "can a Renesis safely make peak power at 9k rpms" and the secondary question "can the Renesis make peak power at 9k rpms with a non-laggy turbo that also makes power down low (3k rpms)", the answer to both is an unqualified 'YES'.

If someone needs a dyno instead of mathematical proof, then contact Mazda Maniac & work with him to find a customer of 'Satan's Hairdryer' & the Cobb Accessport; then pay said customer for some dyno runs.

As an aside, I grew up in Europe so I don't think I qualify as an insular American either.

ttfn

staticlag

Actually we are talking about 9000 on a dyno with a signal taken from the coils.

staticlag

Further proof of what I said is this:

Look at the high HP dynos we have here.

The higher the HP is the lower the peak HP appears at.

This is because of exactly what I said. That those guys are cramming tons of air and fuel molecules into the engine to make that power, that means more stuff needs to exit the engine. This is further hindered by the fact that as the engine turns faster the ports are open for less time. So you have more molecules and less time for them to excape though the 90 degree bend in the exhaust ports.

Brettus

iTrader: (2)

Thankyou for bringing the topic at hand back to the fore .

I would argue that you just need to look at the dynos posted in the FI dynos thread to see where peak power is generated . All the turbos including the 3071 peak at 7500 or below .
Is it possible to get the peak at 9000 ? I don't really know and if you have maths to say that it is possible then maybe it is . But all turbos so far have peaked well below that , so for all intents and purposes this is the current paradigm that exists for the renesis.
So if someone asks you "at what rpm does a turboed renesis peak at ?" the answer is pretty clear cut if you base it on what has currently been achieved.

rotarenvy

9k on the tach isn't correct but 9000 is the std rev-limit and it will reach it.

to get peak power occurring at 9000rpm I'm guessing you would need at least one of three things.

the pr would need to be increasing as in a centrifugal supercharger to over come the dropping efficiency after about 7500 rpm

the turbos efficiency range would need to extend far enough to the right so at high rpm the map is providing cooler air @ the same pr

you port the engine to retain volumetric efficiency after 7500. I think I have read that peripheral ports work better at high rpm

paulmasoner

iTrader: (1)

The GT3071R doesnt make peak power at 9K rpms. As some one has mentioned, i suppose with tuning and boost control tweaking you could basically cut down power in lesser rpms so that your peak is at 9K, but it wont make peak power at 9K without forcing it to. mysql should know, he had it, now i do.

mysql

Here's an interesting graph.

The two red lines are hp and tq with no boost controller, 6 psi. This means it's on a spring, with it allowing exhaust to escape at low rpms because the WG door slowly opens as boost increases.

The two blue lines are 9 psi with a boost controller turned on.

The two green lines are 9 psi again (maybe a less because I was changing all the settings on the boost controller).

Check out the curve of the power and where it peaks. I wish I had a 14 PSI dyno to slap on top of the other three.

Clearly the 6 psi (spring) is peaking at exactly the same spot as the 9 psi runs. 9 psi is making much more power and flowing more air, yet the peak doesn't change.

mysql

^ Anyway, my point with the graph is that if peak is dictated by max flow through the exhaust ports, why is 6 psi and 9 psi exactly the same?

Brettus

iTrader: (2)

/\ yes , very interesting .
You will note that the SCs all peak at 8500-9000 which is because the boost they run is increasing the whole way to the redline and the peak number is still relatively low (as compared to the turbos)

The SC guys are only just cottoning on to this and going for more psi lower in the rev range . They should be setting their pulley size for max boost at around 7500 and not even bother reving any higher (due to SC limitations )

mysql

Yeah, let's see some 13-14 PSI pulls on a SC to compare.

Brettus

iTrader: (2)

The guy who did the 330whp run was running close to that - if you look at his torque curve it is actually getting pretty close to the turbos

would be worth getting it on FI dyno chart as a matter of interest

mysql

Maybe at 9k, but no where close for power under the curve.

The turbo guys are making quite a bit more power and torque through the entire rpm range and don't need to flog it to 9k.

staticlag

I'm willing to concede that at lower power levels it isn't as evident. But Still the ports are the rate limiting factor.

Brettus

iTrader: (2)

transpose the 330 pettit torque curve onto your own - you may get a surprise . Its not quite there but surprisingly close ...

mysql

245 tq at 9 psi?

it's the same car. one solution is more efficient than the other. So no shock with the results.

the stock pettit kit is 7-8 psi, so the bigger pulley they're using is beyond my 9 psi dynos.

in fact, from what I recall, even with the bigger pulley and more boost, they're only just starting to match the peak torque the greddy kit makes.

Brettus

iTrader: (2)

That is true . They have to run higher psi up top to get close down low .
But now that they have twigged onto the fact that they don't have to run all the way to to 9k they are getting better numbers across the board .

mysql

yeah, and soon they'll figure out if they could somehow setup the blower so it's not tied to engine rpm, they could spool it up down low too, and then have some sort of .. wastegate to bypass the blower to prevent overspool at high rpms! Yeah. That would be awesome if someone could figure out how to do exactly that. Maybe their results would more closely match the turbo results.

Brettus

iTrader: (2)

/\ good point heh

r0tor

iTrader: (1)

and then some people figured out that to use a turbo to its full extent, it has to be gigantic and poor spooling. Then they figured out they could use 2 turbos together - a small one for bottom end and a larger one for top end. Then more people found out from that its just too damn wacky and unreliable so they switch to a single turbo again. But then soon enough people began putting superchargers in with there single turbos since the two go together nicely. Then more manufacturers began investing in superchargers and next year Ford, Audi, VW, and Mercedes will all offer very efficient supercharged engines....

this thread is the lamest of 2009 by far... i only hope i just made it more lame

mysql

For this engine, 350 is only as far as i'm comfortable with. There's no reason for me to invest in twin charging, dual turbos, or anything extravagant. I will also go on record as saying that for the vast majority of the rx-8 folk out there, under 400 is also their ceiling.

When efficiency matters... how many diesel trucks have you seen supercharged? Now how many turbodiesels?