How do superchargers hold up to endurance racing? (1.6l Miata content)

After flogging the 1.6l Miata @ Watkins Glen for the past 16 hours or so of racing, it became apparent that an extra 40 or 50 HP or so would do wonders.   There's obviously multiple paths to get that 40 or 50 horsies corralled, but we were thinking supercharging might be the easiest.   Looks like you can pick up a 1.6 JR supercharger setup all day long for well under 1k, even with a rebuild that's fairly cheap.   The car's 1.6 is strong and standalones don't count against our budget in Champcar. 

Other options include swapping to a 99+ engine (140 hp/119 tq vs our 115 hp/100 tq), but that would still require some more doing to get more powah.

From what I've read, dyno at the wheels for a supercharged 1.6 will bump you from somewhere in the 90ish hp/80ish tq at the wheels to somewhere around 130/120, which would hit our goals.

Do they hold up?

Rotrex C30-74. Holds up fine for endurance racing. 

Also consider a VVT swap. I made 150whp with a Header/Intake VVT on MS3

Don't forget the increased fuel consumption that comes with it.  If you can't make 2hrs on fuel, 40-50 more hp won't offset 5-10min of add'l time that extra fuel stops add to your race.

I know nothing about the JR kits, but I would imagine for endurance racing that you would need increased fueling, cooling, and maybe brakes.  IDK how inherently balanced those SCs are -- you might want a new or upgraded crank dampener.

Keep in mind a way to quickly remap and/or bypass in case of SC failure?

The unfortunate side-effect of adding boost is that if 40hp feels good, then 80hp feels better.  Next thing you know, you're looking at turbos.

The old Jackson blowers heatsoak really bad, so while it might hold up for endurance racing, you'll just be making stock 1.6L power a few laps in (although you will get cool sound effects at least). You could maybe vent the hell out of the hood and run water/meth injection, but that's just crutching an inefficient setup. Like goingnowherefast says, the Rotrex supercharger is a much better option, although its definitely pricier.

I can’t think of a single car in Lemons that has added a junkyard supercharger and had it work out well overall.  Turbochargers are a bit better, as there have been a few successes with plenty of teething problems along the way.  We added a turbo to our Honda D16 for the same reasons you did, and at first it exposed issues with cooling, and now we are trying to keep motors together for more than 3 races.  When it runs well though, wow, and we have set fast lap of the race and second overall.   Expect that you will have several races of sorting it out and plan to break several things in the process. 

I have a N/A spec miata 1.6L that is making close to your end power goals already.  

I'd suggest sending your head off to a reputable SM motor builder and have them build you a cheater head.  Mike Rossini does my motor work (mine's SM legal by the way).  

You might spend the same amount of money and not lose any reliability.  Or maybe you could find a used complete race motor on the Spec Miata FB marketplace pages.

In this situation, the Rotrex is simply a turbo with the added excitement of potential belt failure It's going to act like a turbo otherwise.

My concern with the M45 is the same as NickD's - they have a really hot output. Venting the hood won't help, you really need an air/air IC which can introduce some throttled volume problems. That may not be an issue on a racer.

Keith Tanner said:

In this situation, the Rotrex is simply a turbo with the added excitement of potential belt failure

Or a turbo without the excitement of contaminating your oil supply if it fails or a coolant or oil line leak that blows up your engine 

Usually if a turbo fail, the oil supply is the least of your worries!

Keith Tanner said:

Usually if a turbo fail, the oil supply is the least of your worries!

True. Honestly, between Rotrex and turbo, they both have their strengths and weakness and it really comes down to what user preference. You play with turbo Miatas for a living, hence your preference. I have a C30-84 that I love, hence my preference. I think we can both agree though, that either whips the tar out of an old JRSC.

Yeah, I knew about the roots inefficiency/hot output, but I figured that could be dealt with by an air/air after cooler.

We've run turbos for these events before on a different car, and had all sorts of fun failures (turbo separating during a red flag which then burned up the master cylinder, exhaust studs failing, manifold studs, etc). 

This sounded simpler to deal with overall and even easy to deal with if it fails.  We also don't be much power, I doubt we'd be looking to pick up 80hp instead of 40-50ish.  More weight reduction should get us that delta.  We just want to be able to accelerate out of the boot without being a danger.

Fornetti - we just got this engine which is supposed to be a fresh rebuild, so we're going to not tear it apart.. it seems that teams that build an engine rarely finish well.  But, like Sonic says, when it works, it works well!

NickD said:

Keith Tanner said:

Usually if a turbo fail, the oil supply is the least of your worries!

True. Honestly, between Rotrex and turbo, they both have their strengths and weakness and it really comes down to what user preference. You play with turbo Miatas for a living, hence your preference. I have a C30-84 that I love, hence my preference. I think we can both agree though, that either whips the tar out of an old JRSC.

I play with turbos, centrifugals, positive displacements and just plain displacement. Don't confuse cause and effect - we carry stuff because we've chosen to carry it, not because we have no other alternatives. But yes, whips the tar out of an M45, no question!

Ecotec.

solves the HP problem without the headaches of forced induction.

KyAllroad (Jeremy) said:

Ecotec.

solves the HP problem without the headaches of forced induction.

Sounds like that would cost more than a grand or two and take a lot more development & shakedown to get working reliably..

The point of the exorcize is to get an additional 40 hp or so as simply and reliably as possible.

As soon as we swap to anything, might as well just do an LS swap with a turbo, right?  :)

Possibly. I didn’t do mine (see the trade for the horrible no good monster) but it looks remarkably straightforward.  Uses the Miata trans and rear end.  Uses all the GM electronics and engine management.  

LS swaps are for people with deep pockets and/or serious fabrication skills, the ecotec and K miata swaps are pretty simple.

Keith Tanner said:

Usually if a turbo fail, the oil supply is the least of your worries!

Pretty much what I would say.

Frankly I would think that better tires and brakes/suspension would make you faster in the long run and more reliable.

I think for endurance racing you are going to find that the 1.8 swap 99+ "supermiata" recipe is going to be the cheapest and most reliable option. None of the cheap supercharging options will really help you due to the aforementioned heatsoak. And I honestly think you will spend more even garage fabbing a turbo/supercharger setup than you would building the 1.8 so run the 1.6 into the ground and accept it as is or see what you can get for it

The caveat being maybe if you have to build the 1.8 the ecotec becomes viable, they have a DIY kit and are running around in multiple chumpcars

Rotor type compressors introduce a lot of extra heat to the air, a lot more than a turbo with same amount of boost.

There used to be graphs on the Eaton website that showed how much HP was required for boost vs RPM.

That HP wasn't just friction, it was mechanical energy being turned into heat due to chewing up the air.

A good intercooler will make a big difference, many use a small air/liquid type integral to the intake manifold to help address the throttled volume issue

that Keith mentions.

But if you don't get greedy, a blower making only 3-4 psi can yield a solid 15-20% torque & power bump over the whole RPM range, without heating the intake

air very much.

An M45 is 750 cc (45 cu in), so a 1.28 pulley on a 1.6L motor would yield approximately 3 psi of boost, nearly 20% more than NA (remember it's a 4 stroke).

Trackdog does make an intercooler setup for the JR M45? maybe that would do it? maybe? Seems like if it was that simple it would be way more common however. Seems like most the dynos I see of them when setup put down around 145hp and 130's torque

http://www.clubroadster.net/vb_forum/58-forced-induction/21260-track-dog-racing-intercooler-jrsc.html

Reviews are generally good but you are then at 1k for the SC and 900 for the IC

The ecotec racers diy swap kit is 950, the whole shebang is just shy of 2k, the le5 motors are around 1100 but easily do 170+ na and over 200 with light work

Here is another older miata.net post about that IC setup

"I couldn't get past 150hp on my 1.6 with M45 and no intercooler. With the TDR intercooler and a LINK ECU, I am at 185 RWHP. You can see my car in the pics of the intercooler on both Moss and TDRs site, as Gary used my car as the 1.6 prototype. You get the intercooler, pipes, brackets, ducting, hardware, and world class support... Well worth the money IMHO. "

Sorry, why did my VVT swap suggestion get shot down? 

Buy a used 1.8L VVT engine = $800

Intake from Siliconeintakes.com= $20 (PM for parts)

RB or Ebay header=$150-350

Make 140-150 whp all day, reliably, without using much more gas and producing more heat. 

goingnowherefast said:

Sorry, why did my VVT swap suggestion get shot down? 

 

Buy a used 1.8L VVT engine = $800

Intake from Siliconeintakes.com= $20 (PM for parts)

RB or Ebay header=$150-350

 

Make 140-150 whp all day, reliably, without using much more gas and producing more heat. 

It didn't get shot down, but it didn't answer the question of supercharger longevity, either...

clshore said:

A good intercooler will make a big difference, many use a small air/liquid type integral to the intake manifold to help address the throttled volume issue

that Keith mentions.

The reason I didn't mention air/water intercoolers is because they have a tendency to heat soak during extended track use. It's tough to get rid of the heat.

The M45 was originally intended as a 6 psi kit on a 1.6, and was just about the perfect size for that. Trying to push it harder will get you more heat without a lot more power. Accept its limitations and work with them.

Having driven a 1.8 N/A with a cam at the Watkins Glen Chump race two years ago, I can tell you that’s the way to go.  Just look at all the trouble GRM has with their turbo Miata.

racerfink said:

Having driven a 1.8 N/A with a cam at the Watkins Glen Chump race two years ago, I can tell you that’s the way to go.  Just look at all the trouble GRM has with their turbo Miata.

How much does that bump a stock 99? I have a stock 99 now its more torque I miss than anything I think which is where a positive displacement SC could be fun

My high power naturally aspirated Miata was pretty fun, and as fast as a turbo car on a kart track. Not as fast on a big track. Turbos can make more torque than supers, it's all about setup.

Here's a dyno chart. M45 supercharger vs GT2554 turbo. Same engine management (a Voodoo piggyback), same exhaust, everything. The chart is at altitude so the turbo is a little slow to spool, which increases the advantage the supercharger has at the low end. The turbo also does not have electronic boost control, that's straight off the wastegate.

https://www.flyinmiata.com/tech/dyno_runs/M45_vs_VoodooII_1.6.pdf

The turbo was intercooled, the super was not because it already had enough driveability problems.

GRM is having all that trouble with their turbo Miata because they're trying to have trouble. Seriously, if you saw the turbo they put in there, it was just waiting to explode. It looked like it had been fed ball bearings. Everything is being done to the absolute minimum because it's a perverse kind of fun. Don't take it as representative of what can be done if you really try.