> >>>>> Paul,
> >>>>> Interesting conversation I recently had with the local engine
> >> builder on RX8 Parts and their interchangeability with the RX7.
> >>>>>
> >>>>> He recently built a RX7 racing engine with RX8 rotors - I thought
> >> the RX8 rotors were quite a bit wider ?
> >>>>> I also thought the bearing sizes were different - but apparently
> >> not !
> >>>>> Anyhow all went well until he got to 10,000 RPM when the rotors
> >> were binding on the endhousings, so they shaved (just a little) off the
> >> sides of
> >>>> the rotors.
> >>>>>
> >>>>> He also noted that the rotor side seals were much shorter( in
> >> length) that RX7 side seals. He was concerned about too muck leakage but
> >> they worked
> >>>> OK he can
> >>>>> only put down the extra gap in the side seal ( to the apex side
> >> seals) as needed because the side seals were exposed to greater heat of the
> >> side
> >>>> exhaust and
> >>>>> therefore expanded more! Apparently some people put in bigger
> >> apex side seals to make up the difference in gap.
> >>>>>
> >>>>> Also the apex seals were shorter in height so they cut the slot
> >> deeper and put in Hurley apex seals.
> >>>>>
> >>>>> Speaking of Hurley apparently they have a 2 piece side seals (
> >> very thin) which are very flexible and tough.
> >>>>> I suggested using a bi-metal hacksaw blade and grind it down to
> >> size as they are very flexible and tough - the new hacksaw blades out now
> >> don't
> >>>> break at all.
> >>>>>
> >>>>> Cheap side seal idea if anyone wishes to try it.
> >>>>> George (down under)
> >>>
> >>> -> "Powell, Ken" wrote:
> >
> >
> >>>> George, great info. I have wondered if you could use the rx8 rotors in
> >> an earlier 13b. The lighter rotors would allow us to turn higher rpm
> >> safely. If you
> >>>> are using a PP intake port this sounds like a less expensive route than
> >> a new rx8 engine. Looks like you would need rx8 rotors, seals, and
> >> front/rear
> >>>> counterweights to make this work. Maybe the 86 - 91 counterweightes can
> >> be used if the rotating assembly is balanced. Does anyone know if weight
> >> would have
> >>>> to be added or removed from the counterweights to work with the new
> >> rotors (seems like the weight would need to be removed from the
> >> counterweights to balance
> >>>> lighter rotors but sometimes things don't work like it would appear at
> >> first)?
> >>>>
> >>>> Ken Powell-
> >
> >
> >>> Dave Atkins had a 1993 3rd gen and an RX8 rotor at OSH. They appear to be
> >> the same weight.
> >
> >
> >> Ken,
> >> I think Paul is correct with that assessment, I don't think you need to
> >> lighten the counter weights with lightened balanced rotors. It's something I
> >> didn't think of and will put that question to the 'boys at the shop' when I
> >> speak to them next.
> >> George ( down under)
> >
> > Subtle distinction here George. If in fact the rotors are lighter you do
> > indeed
> > need to change the balance weights.
> >
> > Paul Lamar
-Douglas Fir wrote:
>
> Hi George,
>
> The Rotary Engine Press paper I sent you mentioned the Renesis rotors are
> lighter and illustration should less material in the inner metal walls.
> However it might amount to only a few grams. Can anyone out there weigh one
> for us to confirm it?
>
> Doug in Japan
I can't tell you how many grams but it was about only an ounce or two.
Something less than a 1/4 of a pound. A regular rotor is about 9 pounds.
Paul Lamar
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Here is a listing from the Maztrix site of rotor weights. I also found a RX8 rotor weight of 8.2 pounds on RX8.com. I'm not sure that I trust this
8.2 lb weight- I thought that the new rotors were 8.7 lbs. In any event this is a very significant weight saving.
Ken Powell
Rotor Weight and Compression Chart
----------------------------------------------------------------------------------------------------------------------------------------------------
This chart is included in our Website and Catalog for reference purposes. The weights listed are for production, unmodified rotors.
Engine Year Compression Weight (Grams) Weight (Pounds)
12A 76-82 9.4 4603 10.15
12A 83-85 9.4 4353 9.60
13B 74-78 9.2 5253 11.58
13B 84-85 9.4 5253 11.58
13B N/T 86-88 9.4 4553 10.04
13B Turbo 86-88 8.5 4553 10.04
13B N/T 89-92 9.7 4328 9.54
13B Turbo 89-92 9.0 4328 9.54
13B T/T 93-95 9.0 4328 9.54
NOTE: Weights are approximate, and include rotor bearing, but do not include any seals or springs.
Ken are you using a Mac or something weird like that? Your computer makes hash
out of messages :)
Paul Lamar
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