If i was to do it all over again I think I'd give the Rx8 Performance kit a whirl...... The Greddy is awesome, but it does leave you wanting a bigger turbo.....

 

what are you refering to ?

 

my first post in this thread. I could have given info in a nice manner.

 

Why? what results have you seen that I haven't? Just curious.

 

^ Honestly, not much more than Gregs build..... but.... still a low mount, better manifold, bigger IC, comes with a quality BOV and flange already installed and if I understand correctly the turbo on that kit is better suited to the renny than the Greddy T618Z (will hold boost to redline).... I think the kit itself would be well worth somebody's time if they were starting a turbo build from NA, especially since getting your hands on a complete Greddy kit is not always the easiest anymore. I'd say the thing I like the least about it is the MAF placement... only because it would require extending the Maf wiring and I am scared of electrical

 

Theory, not observed results:

rx8performance manifold has a larger turbine flange than Greddy so you can run a larger turbine housing to reduce exhaust port backpressure. Also external wastegate means exhaust gas for the wastegate and turbine wheel won't fight each other for space in the turbine housing, so gives more effective flow to drive the turbine/compressor wheels.

Also less exhaust port back pressure is healthier for the engine and means a few more psi of exhaust expelled from rotor housing each cycle and therefore room for a few more psi of air/fuel on the next intake cycle.

 

True on all counts . Plus lower IATs . But for some reason we haven't seen much in the way of results from this kit .............. I'm sure we will in time though.

 

Well if it's one thing that owning a turbo RX-8 has taught me is that theory doesn't mean ****,

 

Wait, with 0 overlap it should expel almost 100 percent of exhaust.

I can see how less back pressure slowing the rotors will give more power.

Where is my thinking off here?

 

Example
If the back pressure peaks at a bit more than 15psi in the manifold at the end of the exhaust cycle as the exhaust port is closing, this would leave about 15psi (2 atmospheres) worth of exhaust gas volume in the chamber once the port closes, and this volume of exhaust gas would of course still be in the chamber when the intake ports open, so less fresh boosted intake charge will flow into the chamber, meaning less power and more chance of detonation from existing hot exhaust gas in the chamber.

Compare the above to a back pressure of 7psi that might be more typical of a larger turbine housing, you'd get more intake air into the chamber during the intake cycle giving more power with less chance of detonation.

That's the basic concept. If you're going deeper you can consider peak back pressure and exhaust gas inertia which both come into play as the exhaust port closes, but they work against each other so I've ignored them here.

9k, totally agree about it just being theory. I've read it in turbo books and seen dyno results that indicate that this is the case, but no actual pressure measurements on rx8 turbo setups. I'm interested in getting more visibility of this, so I'll be testing on my Greddy setup in a few weeks once my manifold pressure tap is installed. Details to be posted in my build thread.

My bad for thread jacking.

 

I've also thought a lot about a manifold pressure. I keep thinking once you get enough pressure to reach your psi then the waste gate opens and steady the pressure. With a small housing the flow across the turbine happens sooner to increase spool. But should result in the same pressure to keep it spinning.

The only time pressure would increase over a bigger housing is when trying to push boost pressure beyond the rating of the turbine housing. Then it causes back pressure which has to be held in the exhaust manifold to build.higher boost levels.

But I've never seen any type of corosponding data on flow rates verses manifold pressure with different housing sizes.

 

I think the reason we haven't seen much from this kit is that the initial cost of it is quite high when comparing it to a Greddy and it probably scares most people off, but most people don't understand that the Greddy takes alot of money into it just to get it up and running. One day when my engine blows up..... this is the route I'll go.

The thing I like the most is that he has 4 different turbo options to chose from, allowing users to fit the size better suited to their goals. The workmanship of the kit looks to be of quality nature and if it is anything like the intake I got from him the fitment should be bang on. It's too bad Gregs is so non-existent on this forum nowadays because seeing a dyno would be the final piece of the puzzle in terms of this kit for me.

 

The initial cost is quite high but I think the fact that it is sold and manufactured by a shady character is what scares most off and rightfully so. As for fit and finish, I have seen more poorly fitting parts in person out of that shop than I have quality parts so that is something to consider when ordering a kit that is worth more than a clean well running RX-8 is worth. I have seen the costs associated with fixing two turblown kits here locally and trust me, the last thing you ant to do after spending $6000.00 + on a turbo kit is to pay for more fab work to finish crappy workmanship. As for the performance of the kit, well until someone posts an unbiased review then we won't know.

I picked up a PTP kit and the quality is actually really nice. It will be test fit soon on a parts car and then I will figure the BW EFR and the rest of the piping and changes I plan to make. It should be fun.

 

Most people just getting into FI don't know the "history" of this so I'm not so sure that is a factor scaring people off, at least not newer owners.

Out of curiosity what poorly manufactured parts have you seen come out of there? As far as I see he is mainly a parts distributor and only fabs a few things, like the Greddy intake extension (he nailed mine), a modified rx7 oil pan (haven't seen anyone with this), an aluminum undertray with the availability of additional cooling fans (haven't seen any reviews on this as its not something I am in the market for) and an aluminum radiator (which he had one pre-production unit that didnt have a drain but fitment was just fine).

Chatting with Gregs, his turbo kit had zero fitment issues and last I've heard he is extremely happy with it.


Excited to see you take on the top mount route. Is the PTP kit still available new, or did you find a used one? I'm sure you'll have all your bases covered (you always put alot of of thought into your work and do it properly) with the top mount. What are your goals with the PTP kit, boost pressure wise?

 

Two rotary canister setups that both leaked and had poorly machined fittings and an oil pan that didn't fit and had to modified a lot to fit. And that is just what I have seen locally, I know several others who also had similar issues with the poor quality of the rotary canisters. I have seen the intake in person and the quality is pretty good, but the location of the recirc hose fitting leaves a lot to be desired. The radiator seems to fit but is definitely not drop in and having to remove a standard undertray just to swap coolant would be kind of a PIA to me personally. But I bet it functions well being a Ron Davis unit, although I heard somewhere that they are no longer sourcing them from Ron Davis so who knows, I trust him about as far as I could throw him.

Yeah Gregs seems happy with his kit but I haven't seen anything to indicate it is better than a properly setup greddy kit.

I got the PTP kit used but it was never installed. I will be using the IWG BW EFR (7670) so I will be eliminating the EWG piping and such. I will run the adaptronic and a custom intake setup. Heat management will be key. It will be nice to have the turbo easily accessible. I am curious about the performance aspect but I have been in a top mount turbo RX-8 a few times so I don't think it will be a big deal for my use but we shall see, I may end up hating it,

 

Yeah I believe he has since changed the way the recirc fitting angles into the pipe now, I'm not 100% sure on that though as I had him make one up for me sans recirc tube because I run VTA... I know ricer right?!?

As far as the performance aspects of the Rx8Perf kit yeah, agreed there is nothing saying it is better than a properly set up greddy kit, but I'm assuming you mean after you upgrade compressor, turbine and CHRA, I'm still running the stock Greddy turbo (for 5 years now!) and I'd be willing to wager that the bigger dual BB turbo is going to perform better than that.

Thanks for info on the other items though, the rotary canisters are just a little too tacky for me anyways haha, but I didnt know people were having issues with them. In my limited transactions with Scott though I've had nothing but positive experiences so it's easy for me to take a neutral stance on the situation.

And I think your right about the top mount set up, I would give up a couple 100rpms of spool if I could boost all the way to redline as I don't track my car and it would better suit my driving style. Heat management will be the biggest thing to deal with for sure, but if that can be controlled effectively think of how easy it will be to work on that turbo! And don't leave out bling factor, bling factor counts

 

Yeah, once dishonest always dishonest, character rarely changes and I deal with criminals every day. Oh and bling definitely matters and people won't be constantly asking me where my turbo is,

I don't think spool will be an issue with the BW, but we shall see. Going top mount/E85 will require a lot of changes so I won't start until I have everything on hand. In the meantime I really enjoy the car as is and plan on visiting Steve Kan one more time soon on this setup to see what my real potential is.

 

Yeah I thought I would be doing an upgrade to my Greddy turbo next year, but I now have a wedding/honeymoon to pay for so I will be limited to new wheels and MS sides only Priorities, the Greddy turbo still runs 100% so....

Also toying with the idea of removing my S-Techs and selling them with my still uninstalled Koni Yellows and pulling the trigger on a set of PSS9's.... but $2500.... will just have to wait and see how much rubbing I get with the agressive wheels I have planned first.

 

What ever happened to tradition? I always liked the idea of the brides family paying for everything.

 

lol dont you have a daughter 9k?

 

Oh yeah, f%^k tradition.

 

 

I will be really interested to see how mine (when i get my new engine back) will compare with that setup . I think I'll have top end edge but will be really interested in how a top mount with that turbo will spool up.

 

I kind of want to rebuild the engine at the same time but I still have decent compression so we shall see. It will be a while I am getting some body work done first and then I have to fit the piping and get everything coated, etc.

 

Have a read of this thread ........ if you haven't already .

BW 7670 REW and Syvecs dyno resuts - RX7Club.com

It's interesting that everyone agrees the 7670 is too small ....yet it gets the results and nobody seems to find a compelling reason not to use it .
I still think it's just ........................... wrong for the Renesis.