I am in the process of removing my TO4E and fitting a Vortech Supercharger to my TII engined kit car

Has anyone any experience of this? any advice?

 

i used to have a paxton SN89 on my na. it was really fun but ended badly (my own fault). most of the ppl with sc'ed rotary experience and not centrigugal types tho. i know that there is a small following with superchargers (i believe centrifugal and positive displacement types) in the rx8 community, but that'd be a whole other animal when compared to a 13bt.

 

Heaps of kits for Rx8's for them (most of these are Aussie)

http://www.performancedesign.com.au/...arger_kit.html

http://www.rotormaster.com.au/subPage.asp?cid=50

http://www.rx7store.net/Pettit_Racin...tage%202cs.htm

http://www.mazfix.com.au/perfproducts/rx8_upgrades.html

http://www.dnamotorsport.com/ProChar...8_Kit/RX-8.htm

 

I believe most of the SC cars on this forum are using a Camden unit, and a lot of them are running carbs as well. I like the thought of a SCed RX-7, but its hard to choose them over a turbo since rotaries are so good at spooling up even large turbos such as a GT4202.

Why the switch? A small trim T04B/E can spool pretty damn fast on a 13BT and the Vortech isn't a positive displacement unit.

 

Why bother with a Centrifugal style charger when you could have this......... (see pic)


Though the truth is, why anyone would put a supercharger on a rotary is beyond me. There isn't an engine in the world that produces the exhaust volume that the rotary does (for it's size). To not join a turbo to it is a down right sin

-J

 

Plus alot of people deadwall with power using a supercharger after alot of inital investment. Where as with a turbo car there is ALWAYs room to upgrade.

 

who said it was?

+1

+100. thats why i ended up ditching the sc. i had had a 325hp TII before and loved it, then when i got the na i first wanted to do a monster na build. about halfway threw that i came across an excellent deeal on the paxton, so i went that route. $2500+ later i realised i could have twice the car for the same money. so i went from 220hp to 350hp for less money. now i decided to go a little farther. had i kept the sc i would not have been able to do this w/o a ton of fabbing and extra money.

theres power to be made with blowers, just that dollar for dollar you wont match a turbo setup on an rx7.

 

Interesting, many of the problems that I read about on the FD cars stem from the heat etc. associated with the exhaust (I guess the same reason they spool turbos so well). with a SC you can use a nice tubular header and get the heat away in a hurry. Plus isnt the boost on a SC more predictable???

If you had modest power goals it seems like an interesting option.

 

i spose i should put things into perspective.

The engine is in a kit car that only weighs 650 kg's so ultimate power isnt my goal. I had 400 fly with the to4 e and it was too much, i had to fit the biggest wastegate possible to keep a usable boost level. The car is mainly used for track days so i want a nice a smooth power graph and although the to4e was smooth for a small single turbo i think a centrifugal s/c would also give me that option.

Most importantly, the supercharger is free! it belongs to a friend who has stored it for a couple off years after finding it was a bit too small for his 20b and went for a procharger but for other reasons has not completed the project.

He is itching to see if a Centrifugal S/C will work well. I'm not hoping for more power, just a different type of power and we like playing and trying to be different.

And as my TO4e needs a little TLC to the turbine wheel since munching a tip seal, i thought why not. I will do all the fab myself and i can always swap back in a couple of hours if its crap.

From a theory point of view, rotaries like boost which this will give but dont like the exhaust being blocked up which this will not do. Yes rotary exhaust gasses are ideal for spooling turbo's but there is always the compromise of lag. I have had T88's Hi Flow twins, GT35/40, TOO4e and S in all types of rx7 and they are all good in different ways but even with the TO4E i can still light up toyo 888 tyres in 3rd gear which at over 100mph is quite scary.

When i first built the kit car i ported the engine and used the stock turbo II turbo and on track it was fantastic, no lag what so ever made it lightening quick with only 320 bhp but after 5k rpm boost and power would drop off. I still ran an 11.7 quarter with a slipping clutch in a car designed to go round bends.

 

not only is the rotary exhaust great in volume it is much hotter than a piston engine... the turbo gets a lot of its power from exhaust heat making turbos ideal over a supercharger. if more power isnt your goal but better response is a supercharger is probably a good idea but dont expect alot of power at higher rpms either

 

the problem with FD its the turbos are downright trash (sadly still have mine) 22LBS of cast iron bolted to aluminum rotor housings. They didn't left-hand thread the nuts that hold to compressor impeller on so over spinning them results in the nut shooting off and grenading the compressor assembly shooting shards of metal into your intake. the list goes on, a efficiently sized single moves more CFM at lower PSI with MUCH less heat. single turbos are awesome!


once upon a time back when i had my first FC i wanted to do a S/C project, after searching, and sifting through dyno charts and build threads it just came down to the fact that its completely useless on this engine.

 

Most of the time I've seen people choosing a SC over a turbo they're after torque everywhere in the power band and like the instant response.

I can't give any SC advice but, as far as turbos go a BNR Stage 1 or 2 sounds like it would be just right for your car. So long as you have the TII manifold it would be a simple bolt on.

 

i have to agree with staticguitar. blowers have their place, and its not on rotaries. IMHO, if you have modest power goals and favor quick reponse and low end power id say go with an appropriately sized turbo.

also, as quattro pointed out, the main aim of those going with a s/c is low end power. with this in mind, you should know that centrifugal s/cers provide a similar powerband to turbos. altho admittedly not as laggy as even some small turbos, and the boost is produced much more linearly, they are definately not low end power providers like positive displacement types. at least thats my wxpweiwnxw w/ them

 

https://www.rx7club.com/forum/showthread.php?t=431570
http://www.geocities.com/boatseason/rx7.html

 

nice links!

 

^Seconded!

To me the place for centrifugal SCs are cramped engine bays, cheapness (versus a turbo conversion on a v8), and adding mid range and top end to an n/a motor.

 

Heat dispersion is one good reason, but a better one would be eliminating the “brap” (I explained what I mean in an other comment here somewhere), which could aid efficiency and power.

But yes, heat is another nice point.

However I don’t think I’d go for modest power with that level of cost and engineering…

Cheers!

 

This thread is 13 years old. This is your first ever post and you're referencing other posts you've made here. The "brap" has nothing to do with the turbo, SC, or lack of either.

Not sure if you're a bot or not just yet... at least you didn't hyperlink in some phishing site. Yet....

 

The “brap” is caused by the exhaust gasses flowing into the intake ports (and manifold partly) during overlap. It could be eliminated by supercharging (it couldn’t in NA or turbocharged configuration), as the intake air would provide high pressure (higher than the shamus gases) at low revs (where exhaust suction is insufficient) and wouldn’t affect high rev air flow.

Yes, these are my first posts, because I’m young. However, I’m old enough to know what I’m on about…

Cheers, blokes!

Ps: If you wish I can go into more detail on the infinite possibilities of supercharging in another post…

 

You clearly don't know what you are on about, brap isn't at wide open throttle, or at an engine speed where a conventional centrifugal setup is making useful pressure. If you are at low rpm with a partial throttle there won't be a positive pressure differential across the intake/exhaust ports. Unless you are going 2 stroke diesel style exhaust blower which would be dead in 2 minutes and detrimental compared to running without it at WOT.

 

it’s a thread on rotary + SC; where else would you expect this?

 

First of all, thanks for the insult.

Secondly, I won’t explain my point, which isn’t as bad as you might think, if you’re not willing to listen. The effect I’m talking about, achieved via supercharging (I never specifically said centrifugal, even though it could work), has already been experienced and tested on piston engines. The result is useful work produced during the intake stroke (i.e. more power) and better flow (i.e. more power), plus better heat dispersion and a sound some might enjoy.

I hope you’re not just trying to be rude and pretentious. If I am wrong please tell me by explaining your point thoroughly, so I can actually understand why you’re criticising. I’m just trying to help and learn something around here…

Cheers, blokes!

 

Are you referring to miller cycle engines? (letting the s/c do some of the compression)
If so I don't think that translates to rotaries
Also there is a geocities link in this thread. Does knowing what that is/was make me old?

 

... been doing this a long time and am doubtful that you'll come through on your end, but you can count on me to uphold mine.
.

 

(I intend the next 3 sentences in a funny way) ABSOLUTELY ******* NO. The miller cycle is for pussies. It doesn’t make any real power.

I’m on about a different phenomenon, one which can cool down the engine, make it flow better and increase torque. There are 2 effects involved: he first is that the high pressure intake charge is pushing cool air in the combustion chamber, pushing exhaust gases (which are able to flow unrestricted) out together with part of the intake air. This makes everything more efficient, which increases power. The second effect is sort of a “windmill effect”: the intake supercharger is pushing air in against the piston (or rotor), producing torque (which increases power). You can clearly see the possibilities of such a configuration.

If anything sounds confusing, please let me know and I’ll explain better.

Cheers, blokes!