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[Calum]

Originally Posted by moto-mike

We can alter the boost down low with cam timing by letting the blower exhale with a partly open exhaust valve towards the end of the stroke. Reduces boost by several psi. We can also drop timing down low to cut down on power, so that portion is no big deal. But the big blower will eat HP and add weight, so any gains from the cooler charge will be lost. Stock motor I see no issues with 70mm and cooler or e85, or the 72.5 if you want to stay below the continuous redline of 15000 rpm at all times.

Excellent point Mike, I didn't think of it that way.

[tech4pdx]

Originally Posted by moto-mike

We can alter the boost down low with cam timing by letting the blower exhale with a partly open exhaust valve towards the end of the stroke. Reduces boost by several psi. We can also drop timing down low to cut down on power, so that portion is no big deal. But the big blower will eat HP and add weight, so any gains from the cooler charge will be lost. Stock motor I see no issues with 70mm and cooler or e85, or the 72.5 if you want to stay below the continuous redline of 15000 rpm at all times.

3.5 pound diff between the 210 and 335 is hardly an issue (weight of Laminova not included). I shaved significant weight from the front of my car to offset any weight gain. Small blower or big, we know there is a parasitic loss. We know that turbos are more efficient. It's not the point. Nothing screams awesome like a twin screw (or roots) towering over the motor, like a parasite (taking from and giving to its host).

Built motor for reliability.

[R2]

Are there tell tale signs that you are pushing too much at low RPM? I'm curious what the technique is to produce as much low RPM torque as possible without risking damage like what is shown above.

Originally Posted by moto-mike

We can alter the boost down low with cam timing by letting the blower exhale with a partly open exhaust valve towards the end of the stroke. Reduces boost by several psi. We can also drop timing down low to cut down on power, so that portion is no big deal. But the big blower will eat HP and add weight, so any gains from the cooler charge will be lost. Stock motor I see no issues with 70mm and cooler or e85, or the 72.5 if you want to stay below the continuous redline of 15000 rpm at all times.

[EAGLE5]

Originally Posted by R2

Are there tell tale signs that you are pushing too much at low RPM? I'm curious what the technique is to produce as much low RPM torque as possible without risking damage like what is shown above.

When your engine blows or axles break.

[Xero-Limit]

Originally Posted by tech4pdx

3.5 pound diff between the 210 and 335 is hardly an issue (weight of Laminova not included). I shaved significant weight from the front of my car to offset any weight gain. Small blower or big, we know there is a parasitic loss. We know that turbos are more efficient. It's not the point. Nothing screams awesome like a twin screw (or roots) towering over the motor, like a parasite (taking from and giving to its host).

Built motor for reliability.

Can't agree more, but the parasitic drag will be more significant than the weight. As a long time turbo purveyor (this is the first SC car I've actually kept more than a few weeks, though driven and tuned many) I'm loving this SC even having driven/tuned the various turbos...the SC'd ones are v8 like, not turbo 4 cyl. Only reason to go big blower on a stock motor is for reliability of the twin screw; but even that has yet to be proven as a necessity. And the 210 is fairly cheap, so even if they eat their bearings after 50k it is not a big deal. But I'd assume they're running ceramic bearings, so I wouldn't be surprised if we go a good deal longer.

Originally Posted by R2

Are there tell tale signs that you are pushing too much at low RPM? I'm curious what the technique is to produce as much low RPM torque as possible without risking damage like what is shown above.

This question is difficult to answer. The only engine failures we have seen on the NC mx-5 (another high CR boosted platform) were below 4k rpm. But were pushing nearly 15 psi with 2860rs disco potatoes. The 210 SC makes 5-7 psi with a 70mm pulley at 4000. FT86 internals look stronger. We run the MX-5 PD SC cars with tiny pulleys to make the same 12 psi the 70mm makes and 0 failures there. There is the tip-in knock or phantom knock issue with FI on the FT86 below 3500, but I've not seen a single one we tuned go. Ours we pushed to the limit with e85 and aggressive cam timing and doing fine so far. With the header, full exhaust, big intake, cold weather....we have to be at 300whp by now. Figure 350 if it was turbo when you factor in the SC drag on the motor.

So if we went with the bigger blower, you'd probably get 20hp less but with maybe a tad bit less heat at the top end, but at much higher cost for the same boost. If you were to go fully build the motor though with low CR, then that big blower should take you to 400whp or so, so figure LS1 territory p/w. But good luck with the trans and axles then with sticky tires that can hold that power.

No doubt we'd be the first to get the big blower just for the bragging rights, but the 210 with a 70mm is just too much fun as it is!

[R2]

@moto-mike In your tunes for the present 210 SC do you limit torque at low RPMs, say less than 2000rpm using the exhaust overlap and timing retard you mentioned in your previous post? It seems that output there is significantly less than above ~2500rpm, so is this a result of torque limiting or the superchargers lower volumetric efficiency at low speeds?

As a side question for N/A, does the stock ecu tune do any torque limiting at low rpms?

[tech4pdx]

@moto-mike You are a real class act buddy. Thanks for your expertise and contributions to the 86 community!

[Mark@Abbey m/s]

Mike totally agree with the below , the bent roads where from a turbo motor running full boost around 3000/3500 with peak torque around 4 rpm, car was used on motorways (freeways) a lot 6th gear full boost car will spend a lot of time at very high cylinder pressures so we found bent con-rods.

This question is difficult to answer. The only engine failures we have seen on the NC mx-5 (another high CR boosted platform) were below 4k rpm. But were pushing nearly 15 psi with 2860rs disco potatoes. The 210 SC makes 5-7 psi with a 70mm pulley at 4000. FT86 internals look stronger. We run the MX-5 PD SC cars with tiny pulleys to make the same 12 psi the 70mm makes and 0 failures there. There is the tip-in knock or phantom knock issue with FI on the FT86 below 3500, but I've not seen a single one we tuned go. Ours we pushed to the limit with e85 and aggressive cam timing and doing fine so far. With the header, full exhaust, big intake, cold weather....we have to be at 300whp by now. Figure 350 if it was turbo when you factor in the SC drag on the motor.

So if we went with the bigger blower, you'd probably get 20hp less but with maybe a tad bit less heat at the top end, but at much higher cost for the same boost. If you were to go fully build the motor though with low CR, then that big blower should take you to 400whp or so, so figure LS1 territory p/w. But good luck with the trans and axles then with sticky tires that can hold that power.

[Pitman]

Originally Posted by Mark@Abbey m/s

Mike totally agree with the below , the bent roads where from a turbo motor running full boost around 3000/3500 with peak torque around 4 rpm, car was used on motorways (freeways) a lot 6th gear full boost car will spend a lot of time at very high cylinder pressures so we found bent con-rods.

That is an incredibly low peak torque speed, Mark

[Mark@Abbey m/s]

its all about boost management Pitman, running no boost control or bad boost control will cause these issues we seen it many of time son 350Z Turbo motors that also has chocolate rods. You need to control the boost pressure at low rpm levels not allow reasonable boost pressure until highish RPM and even have car speed boost as well.

What numbers did you see with your car on the dyno?

[Calum]

Originally Posted by Mark@Abbey m/s

its all about boost management Pitman, running no boost control or bad boost control will cause these issues we seen it many of time son 350Z Turbo motors that also has chocolate rods. You need to control the boost pressure at low rpm levels not allow reasonable boost pressure until highish RPM and even have car speed boost as well.

What numbers did you see with your car on the dyno?

He was referring to your typo, of 4 rpm verses 4K rpm, I'm assuming.

[Mark@Abbey m/s]

Originally Posted by Calum

He was referring to your typo, of 4 rpm verses 4K rpm, I'm assuming.

oh okay......been looking at dyno screen for too long;

peak torque at 4000rpm worries me now after seeing the con rods.

[R2]

This is the detail I am trying to figure out and understand. How does one go about deciding how much boost is too much for a given RPM? Why is high boost at low RPMs more trouble prone than at boost at high RPMs? Are there documents or white papers that you know of that I could take a look at to wrap my head around this?

Originally Posted by Mark@Abbey m/s

its all about boost management Pitman, running no boost control or bad boost control will cause these issues we seen it many of time son 350Z Turbo motors that also has chocolate rods. You need to control the boost pressure at low rpm levels not allow reasonable boost pressure until highish RPM and even have car speed boost as well.

[Pitman]

Originally Posted by Mark@Abbey m/s

its all about boost management Pitman, running no boost control or bad boost control will cause these issues we seen it many of time son 350Z Turbo motors that also has chocolate rods. You need to control the boost pressure at low rpm levels not allow reasonable boost pressure until highish RPM and even have car speed boost as well.

What numbers did you see with your car on the dyno?

Can't remember the exact figures, but Adrian has deliberately reduced the boost at low RPM to prevent any form of tip in detonation. From memory, it is set for full boost to only come in at around 5000 rpm to protect my engine on 99RON fuel.