nbfather

Interesting thoughts on supercharged torque output. I could see the soft midrange saving parts alright.
The downside to supercharged cars (I have owned a few) is they are hard on the bottom end and have been anything but reliable. Perhaps the Miata (Rotrex) systems are different, but the Miata bottom end seems far from stout...and since that is what drives these things.....I would be apprehensive about 400hp with a blower. That is just my first blush at the thing, and I have zero experience with a supercharged Miata of course.

As far as out budget goes I am aware it is a bit low....I was aware of that day one, but that is the number my son started with. He either has to make compromises or adjust his budget. There is no way we are going to spend 50K though.
I have basic fabrication skills and most of our fabrication plans are pretty light duty. I have friends with serious fabrication skills if we need that, but I am trying to keep fabrication costs down

Puddy Mod! That is the name I was looking for!

I have never heard Miata, 500hp, and hook, in one sentence before?
How is that accomplished?

Thanks for posting!

Cheers,
Jamie

thumpetto007

iTrader: (15)

Are you speaking of the parasitic drag of superchargers? The rotrex has a much higher efficiency than other types of superchargers, but I suppose it does put some amount of strain on the crankshaft. I have read that it actually can help engine harmonics, as it sort of acts as a damper.

I dont have first hand experience with a 500whp miata, but it seems the people that have traction issues (most high hp miatas) aren't using extremely sticky tires. They usually are using 200 or higher treadwear tires. I personally find this ridiculous, and the main reason for the general consensus of "miatas have poor traction" If the tires are lasting more than 8-10 thousand miles of regular street driving, those aren't the correct tires.

However, the miatas that seem to have no traction issues are using M/T drag, and Rival S, Toyo RR, or hoosiers for the circuit.

sixshooter

iTrader: (12)

I'd not try to get 400whp out of a BP engine in a track environment. It would not be reliable. LSX at that level.

thumpetto007

iTrader: (15)

^really? I would think the drivetrain would be an issue, not engine. The off the shelf built engine TSE has for 4500 is rated for 500whp continuous.

nbfather

Indeed we have no intention of going near that power level on the track.

nbfather

Keep in mind these opinions could be totally off on a Miata and that I have Zero forced induction Miata experience...So with that in mind:

When you have a stock 130hp engine and you turn it into a supercharged 400hp engine there is a great deal of power transferred between the crank pulley and the supercharger.
A conventional roots blower that number is around 20%. In a paxton/Rotrex/Procharger that number is less, but it is still significant somewhere in the 50-80hp range.
A 400hp engine makes 100hp per cylinder, then the front front 2 caps, and that section of crank have entire load of the supercharger to that area. Also the crank is turning one way and the supercharger is trying to turn the other way. Keep on mind how anemicly small the crank studs are and how few of there there are....Check out the cast caps while you are at it.
Though the Miata crank is forged, but it is not a great crank and turns to rubber at very high RPMs...Similar to the stresses of high RPMs the supercharger stresses the crankshaft with a counter force...
If you have ever watched a blower belt whip around it is pretty simple to see that the counter loading is far from consistent and even.
Whoever said the blower acts as a harmonic damper is an idiot....Plain and simple.

I have campaigned supercharged engines where after a couple of dozen passes on the dyno the bearings were anything but fresh.
Then I added 500hp to the exact same long block and went turbo....On the dyno and 30 or 40 passes later I pulled the bearing caps...They looked like new bearings with oil on them!
These are pro built and pro tuned motors. The best crank and bottom end that money can buy...the works.
Ask any engine builder and he will tell you the same thing.
I can't tell you exactly what happens inside an engine, but it is much more violent in there with even the best superchargers.
Maybe Miata has some Voodoo magic in there somewhere?

The 350hp car I drove had Rivals and it had serious traction problems with 225 Rivals?

thumpetto007

iTrader: (15)

I'm curious if rotrex superchargers have a similar effect on the bearings. I dont remember the numbers but the rotrex is much more efficient than any other supercharger, and has an exponential boost curve while stagnant parasitic loss.

That's kind of an interesting trade off, bearings or rods.... supercharger or turbo... power loss through parasitic drag or heat...

Were the tires rival? Or rival S? big difference. Age? The 2016 and newer rival s is an improved compound. Suspension setup is important too.

afm

iTrader: (3)

PD and centrifugal pumps are going to be VERY different in this respect.

nbfather

Any centrifugal style blower will create less bearing wear than a roots style at the same horsepower.
My last supercharged setup had an $8000.00 Procharger and after 30ish dyno pulls the bearings no longer looked new....big power, but 400hp in a Miata motor is also pretty serious power.
Same engine, twin turbos, more power, and almost 40 pulls and the bearings looked as new.
Not a huge deal, but it you are planning on a 400hp supercharged track build you better have a plan for regular engine tear downs....Or at least inspections.

All I know was fresh looking Rivals, but if it was the the less sticky Rivals 3rd gear will still be loose with the stickiest tires made. 2nd will be all over the road no matter what tires.
As far as traction goes? Maybe you are talking a smaller turbo or supercharger setup? The torque of the EFR in a well designed system is much (MUCH) more significant. Unrestrained by thoughtful boost/map control the EFR setups would be all but undrivable in the first few gears.....Even with drag radials....and this car will never see those.
Also remember there are guys that are making big power and then there are saying that are making big power...The car is really designed around traction.

Also the car will have 700 or maybe even 800# springs.

Cheers,
Jamie