AllSystemsNominal
AllSystemsNominal New Reader
3/22/13 12:26 a.m.

1.8L engine. Will be turbo'd and using megasquirt. Will be properly tuned

Is a 210-220whp limit low enough to keep the stock connecting rods happy for track use or do I need to lower the power some ? Id just like to have things setup where I can beat the E36 M3 out of the car and not worry about my rods

Keith Tanner
Keith Tanner MegaDork
3/22/13 12:29 a.m.

Properly tuned is the key. Keep it from knocking, it should be fine.

Keeping it cool is going to be your challenge.

z31maniac
z31maniac PowerDork
3/22/13 7:32 a.m.
Keith Tanner wrote: Keeping it cool is going to be your challenge.

That's what I was going to say. After doing all my research on it, I decided against a turbo track car.

Big radiator and fans, coolant reroute, oil cooler, Iconel studs, ceramic coated manifold and turbo.........and you may still have problems keeping it together for 10/10ths driving for a 20 minute session.

GameboyRMH
GameboyRMH UltimaDork
3/22/13 7:56 a.m.

Yep if you want to be able to run it flat out all day and not worry about it then boost is not your friend. If it's gotta be boosted, get a good aftermarket radiator and a serious oil cooler, ceramic coat what you can afford to and heat wrap what you can't.

GameboyRMH
GameboyRMH UltimaDork
3/22/13 8:30 a.m.

You wouldn't have them as bad but once you boost, especially with a turbo, there's a big increase in heat production.

I'd guess you'd be fine with a stock radiator w/ coolant reroute, a decent oil cooler and some heat wrap but Keith might have real-world experience with such a setup.

Duke
Duke PowerDork
3/22/13 8:46 a.m.

The Manic Miata is supercharged, not turboed, but it's running about 10 psi on a stock 100,000-mile bottom end. It does have an aluminum radiator and a coolant reroute, but it was built for track work and will stay around 190 under loads for a long period of time.

Jay_W
Jay_W Dork
3/22/13 8:47 a.m.

I rally what is basically a miata motor. Although it's all forged internals and all, I still really don't want it to overheat. A pair of Flexalite fans on one of those thick hi-cap 160 buck Ebay aluminum radiators means that I can hammer that car with as much boost as we can force through the restrictor and it does not overheat, at least in this PacNW climate.

z31maniac
z31maniac PowerDork
3/22/13 8:51 a.m.
Wonkothesane wrote: Sorry for the threadjack, but do you guys think you would have all those problems with a turbo'd miata only running 5-6 PSI with a small turbo (think 14b or smaller)? I'm talking about maybe bumping a 1.6L from 110 HP to 150ish, hopefully using the stock ECU with a rising rate FPR and pulling timing for excessively cheap performance, trying to hit within spitting distance of chumpcar's $500 valuation..

A bit more expensive, but at that power level goal, I'd rather swap in a 99+ motor, I/H/E + tune and you'll be right around that 150whp mark.

HunterJP
HunterJP HalfDork
3/22/13 9:02 a.m.

Rods will be fine. I was making that power, and never had an issue with my rods, at all. Had all the issues everyone else has mentioned. But the rods looked great, when I went to rebuild the motor because the rings failed. To be fair, at that point, the car had over 150K on it, had been boosted for the last 50K, and I had been running a fairly aggressive tune at 15 psi.

Keith Tanner
Keith Tanner MegaDork
3/22/13 11:03 a.m.

Thick radiators are not necessarily good radiators. Thickness is not a substitute for a good core.

A small turbo will usually run hotter at a given power level than a big one. If you want to keep coolant temps down, you're better off running a bigger turbo at a lower boost level. You'll give up a bit in response, but not so much in the range used in the track.

I'm thinking that a whole lot of cooling problems are due to airflow. Everyone puts a lot of emphasis on big rads (usually cheap big rads, some of which have tested as worse than stock in our testing), coolant reroutes, etc. Basically, you've got three things to do: get heat out of the engine and into the coolant (reroute), get the heat out of the coolant and into the air (radiator, fans, airflow) and have a buffer in the system so you can absorb the heat of a full boost run and dump it when you're off the gas (big radiator).

I think it's the second part we really need to address on a lot of Miatas. That means fans (even on the track) and attention to getting the engine bay pressures down - which means hood vents. Again with fans, there are some craptacular cheap "slimline" setups that barely move any air. You want your fans with big fat torquey motors, a decent distance from the core and a full shroud.

Note that I'm talking about coolant and oil temps. Ceramic and heat wrap are just to protect other things in the engine bay. Inconel studs are addressing a totally different problem.

HunterJP
HunterJP HalfDork
3/22/13 11:44 a.m.

Not surprisingly, Keith is spot on.

I had FM's vented hood, a re-route, and their dual core rad (coolant and oil), and still had issues. However, I think if I would have done a better job of making sure more/all the air went through the rad, instead of around it, and I would have ran a bigger turbo for the power levels I was looking for, I would have been better off. My front end ducting wasn't optimized, and the turbo I was running was pushing it, efficiency wise, at 15 psi. And running lower pressure might have saved the rings at bit, as well. Just a guess.

Dashpot
Dashpot Reader
3/22/13 12:01 p.m.
AllSystemsNominal wrote: 1.8L engine. Will be turbo'd and using megasquirt. Will be properly tuned Is a 210-220whp limit low enough to keep the stock connecting rods happy for track use or do I need to lower the power some ? Id just like to have things setup where I can beat the E36 M3 out of the car and not worry about my rods

^That's my setup^ - 5 seasons with most of upgrades mentioned above.

Listen to Keith, it's his job to know this stuff and he's been at it a while.

A note on cooling - You may live without a hood vent by completely sealing all potential air bypass routes around the rad/oil/intercooler area. A good belly pan with side & radiator fences, side plates cut to match the bumper skin contour, rubber strips/pipe insulation/racers tape to seal small gaps & overlapping seams. You're trying to maximize the differential pressure across the rad and every bit helps.

monark192
monark192 HalfDork
3/22/13 12:30 p.m.
z31maniac wrote:
Wonkothesane wrote: Sorry for the threadjack, but do you guys think you would have all those problems with a turbo'd miata only running 5-6 PSI with a small turbo (think 14b or smaller)? I'm talking about maybe bumping a 1.6L from 110 HP to 150ish, hopefully using the stock ECU with a rising rate FPR and pulling timing for excessively cheap performance, trying to hit within spitting distance of chumpcar's $500 valuation..
A bit more expensive, but at that power level goal, I'd rather swap in a 99+ motor, I/H/E + tune and you'll be right around that 150whp mark.

Im going with the 99+ swap in my 91 for simplicity and reliability. Complete lack of progress is shown here.

z31maniac
z31maniac PowerDork
3/22/13 1:05 p.m.
Keith Tanner wrote: Note that I'm talking about coolant and oil temps. Ceramic and heat wrap are just to protect other things in the engine bay. Inconel studs are addressing a totally different problem.

This is true, but they are still well documented problems, so I thought we should point them out.

Keith Tanner
Keith Tanner MegaDork
3/22/13 1:53 p.m.
Dashpot wrote: A note on cooling - You may live without a hood vent by completely sealing all potential air bypass routes around the rad/oil/intercooler area. A good belly pan with side & radiator fences, side plates cut to match the bumper skin contour, rubber strips/pipe insulation/racers tape to seal small gaps & overlapping seams. You're trying to maximize the differential pressure across the rad and every bit helps.

Definitely, it's all about pressure differential. I think the easy pickings are on the post-radiator side myself - people have been poking vents all over the nose and messing around with foam, but if you don't give that air anywhere to go it won't help. We've got a hood here that's being hacked up in the name of Science! and we'll be using the pressure differential across the rad to determine effectiveness.

I have to admit that our previous vented hood didn't have the vents in the most effective places. We've taken a different look at the aero in the decade since and realized they should be elsewhere.

Personal experience: one of my cars always had trouble staying cool at a 70 mph cruise. We're in a really tough place for cooling here, with high ambient temps, high altitude and low humidity. We tried different radiators (this was before our instrumented dyno cooling test sessions), scoops, ducting, etc. No holes in the bodywork. The thing that made the biggest difference? Good fans. There's really not much airflow across the rad, and even at 70 mph the fans made a dramatic difference.

Dashpot
Dashpot Reader
3/22/13 6:56 p.m.
Keith Tanner wrote: We've got a hood here that's being hacked up in the name of Science! and we'll be using the pressure differential across the rad to determine effectiveness.

Good! The other turbo & high HP N/A Miatas in the club all have some sort of hood venting but I haven't seen any test data to confirm whether they produced real results or not.

My car still has nice shiny original body & paint, and I don't have the gumption to cut it up without a real good reason. Dropping coolant temps ~20 deg. is a real good reason. I'll be looking forward to your results...

Duke
Duke PowerDork
3/22/13 9:18 p.m.

Yeah, my hood has its share of hail damage - I'd be willing to cut a few strategic vent holes in it.

Jay_W
Jay_W Dork
3/23/13 9:23 p.m.

"Thick radiators are not necessarily good radiators. Thickness is not a substitute for a good core."

True dat. Believe me if I coulda routed plumbing to make a miata rad work in a Protege, I'da bought one from FM fer sure! This one does seem to work, at least so far...

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