How come Mazda never used a SC since they started using forced induction on Rotarys in 1986?

 

How come they stopped using turbos? How come the turbos they used were unreliable pieces of junk?

 

MM - I agree with you in saying it was a unfair comparison in that you had to hold the engine against the brake to get the boost happening at the low RPMs. That is why turbo'ed anything drag cars need to be bouncing off the limiter or two-step while sitting at the lights before the green comes on. PD supercharged engines don't need to do that.

Boost Threshold? FFS - It is lag. A turbo must wait for exhaust back pressure to build to spool up the turbine/compressor to create boost, and that is exactly what is happening when it is being held against the break.

If I was happy to drive around at 2,xxx RPM with my foot on the brake and holding the throttle to the floor to put the engine under load to have the turbo spooled just in case I wanted instant acceleration, then I wouldn't have a worry. Or the alternative is I could drive normally at 2,xxx RPM and go to WOT a second or more before I wanted boost. Or I could just mash the throttle and wait.

Like I have said before, I have driven both. I know what lag feels like. I know wat instant torque feels like from my S/C, as it makes instant boost.

To be honest, it is getting quite annoying to have so much theoretical arguments put my what when I have the practical runs on the board. Perhaps I should just monitor this thread and laugh, instead of trying to help with peoples understanding.

Cheers,
Hymee.

 

I guess a lot of people ignored the "What would YOU like" aspect, and turned it into the usual Turbo/SC war.

The funny thing is, that with 120 respondents, its still basically 50%-50%

 

No, now you are putting words in my mouth. I didn't say I had to do anything.
I can develop that boost almost as soon as it starts on the dyno, without load hold.
However, the DynaPack allows you to stabilize before you let it rip through the RPM band, so you can adjust the fuel for those odd and unrealistic driving breakpoints like boosted operation at 2500 RPM.
A DynoJet also supplies much more load on the motor that actual driving, so the result is the same.

No matter how you look at it, the turbo will provide more power in every possible load point than the S/C. That's just how it is and anything else is propaganda.

The supercharger has its place and that is that it sounds cool and has a unique performance profile that some people prefer.

BTW - I had to go do some stuff today, so I tried to drive the car at 2000 RPM. It is nearly impossible. more importantly, in gears that yielded that RPM range in normal driving, mashing the throttle produced 6 or 7 PSI in less than a second.
Now, a positive displacement blower might produce that much boost instantly, but it would be utterly useless and the net power would be near or below stock because of the losses.


I'd be interested to see how many of each camp that voted actually have one or the other.

I'd wager one, fat American dollar that more of the turbo camp actually own turbos than the supercharger camp owns superchargers.

Having experience one way or the other makes the selection preference a completely different matter.

 

Considering that there are maybe a dozen people on this forum that own superchargers, and several dozen that own turbos. It makes for a pretty useless observation. The Pettit kit hasn't even been out for a year.

 

I'll defend both. Today I'm in the mood to argue in favor of superchargers but it depends on the situation. Keep in mind I've owned turbo rotaries. It's pretty safe to say that a turbo will NOT "provide more power in every possible load point than the S/C". This is utterly false. It's a blanket statement that would have you believe that a turbo is ALWAYS superior to a supercharger. This is not true and is something that many turbo owners have a hard time comprehending.

 

From what I under stand is they had a problem with emissions and warranty related issues because of the oil consumption and people not knowing how to properly maintain a Rotary.

I would love to see some 1/4 mile runs with turbo's and SC's making the same peak HP. What comparisons I have are on youtube.com where a Pettit RX-8 is running 13.9's and a $3200 Greddy running 13.1's-13.4's both at the 265-275 rwhp ratings. Thats quit a big difference in ET. The guy did run a 13.9 with his turbo at one point... and that was when he had a leak in his setup...

Have fun with your 50 extra pounds of torque for $6500 in those Pettit applications, I think I will choose the 100+ extra torque from any decent turbo.

 

Actually the turbos were a huge reliability problem for them. The end of the RX-7 in the US as well as other Japanese sports cars at the time was due to the fact that they were priced very high compared to their American counterparts. Sales were poor.

 

Turbos at the strip have the advantage, turbo lag allows easier hookup, where SC puts the torque to the wheels from the dig, but good slicks/suspension might make it a different story. But I always owned turbo cars, I prefer the turbo, besides not much lag on an 8 anyway since it keeps a pretty smooth consistent exhaust.

TO EACH THEIR OWN, either way a FI rx8 is badass no matter how you look at it

 

It was your statement, not mine:


I've already posted evidence that this is not true. Roughly 100% more power at the bottom end in not useless, nor it is near or below stock.

Yes, I see it turning into the tradtional SC v's TurboSC war. I'm trying to stick to the "If you could go..." theme, and defending the claims made against me, or the untruths of theory claimed by others, and backing up my thoughts with evidence as appropriate.

One more thing, if two cars make the same peak power and weigh the same, then they should have almost identical trap speed, no matter what the engine/fuel/induction. It is just how it works. MPH across the line is the measure of power.

Cheers,
Hymee.

 

Every 1/10 of "lag" on the start line is 2/10's at the other end.

Every good turbo car making good numbers is bouncing off the two-step on the start line so the power (boost) is there when the lights come down.

Cheers,
Hymee.

 

I was making the point of how pointless boost at 2500 RPM is.
I was also being polite.
The fact is, the loading makes no real world difference.

Its not "lag". Talk about misinformation.

Hardly. If I even need it, a couple of light revs are all it takes to be in full boost when the tree comes down.

That is absolutely true.

However, it completely ignores the flow penalty and the drag penalty incurred by either system and the S/C will need more power to make equivalent power.
The turbo needs 6 HP per 10 pounds of air. The s/c will need almost 30.
Never mind the adiabatic losses of the S/C.
The twin screw barely makes a 70% island and you are in and out of it in a very narrow RPM band.
The GT3071r turbo hits almost 80% and it is there for almost the entire rev band.
The S/C must work much harder to make the same power and the dollar to power ratio is much higher.

OK, I'll bite. When is it not? At 2000 RPM?

 

interesting...

 

Always!

 

wouldn't have it any other way.

 

on the way home I intentionally stayed in 6th gear to see what speed 2,000 rpm would bring. ugh. Are you kidding me Hymee? You sit around at 40 mph in 6th gear?

I felt like I was doing a disservice to my car by lugging the engine in 6th. No way is this normal driving for anyone.

 

I drive around town in 6th gear from time to time.

 

at what rpm/speed?

 

Hopefully at least 70 MPH!

 

Are you saying if they both make 300 rwhp and one has peak torque of 255 and the other is 195 they will be exactly the same? Because that is what the whole argumant is, the turbo will have more torque. I know you didn't exactly say that but you know as well as all of us that the torque from the SC will be lower so it sounds like you are saying that if they have the same peak hp they will run the same time in the 1/4 mile.

Yeah I already said that, our cars in standard unmodified gearing, for 6th gear you multiply the rpms x .02 and that is what speed you will be at. Or to simplify, you just double the rpms and take off 2 zero's. 4000 = 80mph, 5000 = 100 mph, 6500 = 130 mph and so on.

2000 rpms is ridiculous to drive around at with the Renesis, its almost like idle.

 

Don't go down that path.

HP and torque are mathematically tied to RPM. If two RX-8s have the exact same peak power (at the same RPM), they will also have the same torque at that RPM.

We've already demonstrated that not only does the turbo produce more torque sooner, it also produces more of it everywhere.

The peak HP number (just like the peak tq number) is totally meaningless since it is a single moment in time.
The sum area of under the torque curve is the only thing that ever matters and no one seems to want to talk about that.

So, be prepared to have your assertion bitch-slapped.

 

I see what you mean at that 1 point in time they may have the exact same power but what I am referring to is through out the whole tachometer range the peak torque and torque curve will be looking much better on the Turbo'd car. I guess you have to be very specific or you will get picked apart in these comparisons

This is fun

BTW I will be ordering a Cobb from you very soon

 

Which one of these superchargers has the most area under the curve:

 

Unless you live in wide open roads and streets like drag strips, many of us have to deal with traffic.

In traffic situations, your car easily bounces around in the 1,000 to 4,000 RPM range for extended periods of time.

If I was going to put my RX-8 on the drag strip, than I would probably go turbo and go for the most HP possible. However, street use and track are a different situation.

For the street, you want a car that is great at a dead stop and the red light, good at stop and start again, great weaving through traffic, and will give you less mechanical headaches with "tweaking" and failure.

On the top end, 8,000 or so. The SCs are there too. So you can see a higher stage kit being competitive.

I'm familiar with the feel of the Greddy turbo on the RX-8 because I drove around in an Re-Amemiya one. The lag was there (in my opinion and so was the rush), if you drove both a SC and a turbo (in my case I also drove a Blitz SC, Knight Sports SC, twinscrew SC Mustang, and turbo RX-7s + other turbo cars) , then you know the "different" feeling.

SC feels like a bigger engine and it also feels like a powerful stock RX-8. A turbo RX-8, feels like a small engine + turbo (due to that roller coaster rush feeling and the characteristics of the RX-8 engine). Turbo feels good and gives you a rush, but there is still a difference in how both feels and thus preference.

Now I have not had the pleasure of the MM upgrade, but it's definitely a kit under consideration. In fact I will recommend to Re-Amemiya or R-magic to "tune" in to what is going on here.

In the (NOT independently verified) MazdaManic chart you are comparing different turbo and SC setups that are at different HP and different PSI. A chart that mathematically compares each kit for what it may put out (based on supplied info.) at the same HP and RPM may be interesting to show.

I like data too. But, it has to be backed up with real world drag, track, and testimonials for it to be the "end all" in a debate. The different characteristics of the SC and turbo kits are just going to make that more complicated.

Minus the MM turbo upgrade, your chart also shows why some people would prefer the Pettit kit and/or a higher stage of his kit. Another thing is to notice is how similar the Pettit kit is to stock.

Your chart also is not indicative of what Hymee's SC will do. If you consider the MM upgrage as "top dog" than Hymee just has to get close and at an acceptable HP, because of the different characteristics of SC and turbo and preference for "feel" of one over the other (and possibly other issues like install, maintenance, etc...).