Two reasons im trying not to place an emphasis on horsepower figures are 1. My seq twins have been dynoed at 3 respected tuners with figures ranging over 70 horsepower difference on the same boost level. 2. The US dynos seem to be quite optomistic in relation to our uk ones. Im not saying either is right or wrong just that they are different.

With that said im happy receiving everyones opinions as it helps me draw my own.

" after a hot session on track my compression does get low so takes a bit extra to start"

i remember being close to the GT3 false grid at the 82 Runoffs at Road Atlanta as as the 5 minute bomb went off. Chris Dembs had to start his RX2 by pouring oil into the downdraft Weber carb. the engine immediately started and i believe he won the race. just shows that sometimes if you can get them started they can work well. centrifugal force and apex seal mass come into play as rpms build.

congrats on getting alot out of what came in the box.

Howard

It is the combustion gasses behind the seals that push the seals onto the housings.

"combustion gasses behind the seals that push the seals onto the housings"

i have always understood there were a couple of factors, rotating mass and combustion pressure and your comment got me to noodling.

it appears that combustion pressure is the major factor as apex seal weight against the housings rises from .0183 of a pound (8.5 grams) static to 23 pounds at 9000 crank rpm/3000 rotor rpm not counting the addition from the eccentric which isn't a lot.

combustion chamber pressure behind the seal should deliver quite a bit more force.

Yes, because you have to remember as the apex seal crosses the minor axis on the rotor housing the inertia from its mass is actually forcing the seal into the rotor apex seal slot and it takes quite a bit of gas sealing force to push it back onto the housing surface.

This is why lighter apex seals seal better especially at high rpm!

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During the development of the rotary some attention was paid to ways to more quickly bring up the gas sealing forces behind the apex seals such as these gas ports (grooves) machined into the flanks of the earlu NSU apex seal leading to the back.http://upload.wikimedia.org/wikipedi...-ApexSeals.jpg.

Also, in peripheral intake only engine such as a race engine or the Mazda3 EV range extender a faint depression with the outline of an intake side port is left on the side housing so the sealing gasses can blow down and transport carbon and sludge out from behind the seals to prevent fouling.

also why we get the chatter marks.

At lower RPM, there is more time for combustion pressure to leak.

I can "feel" when I have hurt an engine by how it feels under 3000rpm. The worst I had, you could go WOT in 3rd gear at 2500 and the car just made more noise, no acceleration.

My current 13B has felt "soft" for a couple years now, it doesn't have the low end punch that it used to. But it still makes heaps of upper end power. I think the chrome on the rotor housings is done.

Back to OT, I'm still kind of amazed that the K27 is considered for a rotary at all. The Audi guys like them for nostalgia reasons since the Sport Quattro came with them, and I'm shopping a K26/27 hybrid for mine for just that reason, but mostly they are treated for what they are: slow spooling HEAVY-wheeled turbos that can take a beating but are far outclassed by more modern units in both flow and spool.

Considering the size of the turbo, even with heavy wheels it will probably have full boost in the low 3,000 RPM range which is just fine for what is pretty much a track only car as he'll be above that all the time anyway. And if it's known as a very durable unit then all the better as it will probably last 5-10 years like his OEM twins did on water.

What does boost onset RPM have to do with spool speed?

What I mean is that as long as the turbo has full boost around 3500-4000 RPM and it makes the power you want it is fine for a track car because you are never driving the car below those RPMs anyway.

Just to update this Long LONG day and well over 700 miles covered. No power figures yet but its far in excess of 400+ and a lot more powerful than my twins. Full boost by 3200 and very little tail off by redline. Mapped to 1.25 bar, ill be honest i wanted more but after driving it home i now agree its plenty. The way the boost comes on is violent and for what is essentially a small turbo im very very happy with it.

Quick vid of the spool up in low boost 1bar due to clutch slip at anything higher. The spool actually seems to come in quicker at the high boost setting but either way it's full boost before 3k on either setting.

This was in 4th or 5th gear i can't remember