I'm getting somewhat worried about lag by setting these new turbos up parallel. Especially with a streetport and clipped turbo wheels (which increase top-end power but decrease spooling) this thing might not be fun to drive (in town) unless out on the highway doing powerband blasts. I also have a lightened flywheel which might make it even more a pain to get the car going. Sequential puts more stress on the shafts but Bryan puts a lot of time in balancing all the internals. He said I should have full boost by 4.5K rpms - to me that's waiting around for too long - what do you guys think?

 

4500 rpm is a long time to wait IMO

 

Let me get this straight, the light weight flywheel makes it toughter to get the car going? I would have thought just the opposite. Please help me out with the reasoning behind this.

twstd

 

twstd rx- Lightweight flywheel while increasing hp lowers the torque.

kwikrx7- 4500 does seen like more lag than you would get with a large t4...? How big are those fickin things? Well to be sure, at what boost level are you concidering it full boost?

 

I guess I need a physics lesson or something. It seems to me that less weight on a reciprocating assembly would make that assembly easier to spin.

I'm not disagreeing, I just don't get it.

Screw it. Just get a GT3540 and make some real power. If you can get your hands on one before September.

 

It helps the engine "spin easier" in the high end, but when there is a load on the engine at low rpm (everyday driving) it doesnt have the torque to get moving the low end of the band. So basically with a light weight flywheel you need to be at a higher RPM to get moving than if you have a heavier one.

For instance OS Giken has both heavy wieght and light weight flywheel versions on their clutch assy's. The heavy ones are for drag racing(torque needed) and the light weight ones are for circut(high end hp needed). Got a little long winded but I hope it helped. Jesse

 

Lets stay on topic.

Barry, how much stress will be put on the secondary turbo if you run the sequentially?

 

sorry double post

 

rikki- Light weight flywheels are great, and dont get me wrong the high end gains far out weigh the low end losses especially for an RX-7.

twstd rx- But you DO lose torque(not even enough to be a significant bother but the loss is there). That why it would take longer to spool up but once you get there hang on.

 

Non Seq if your going to actually race it, Seq if daily driving is the goal.

 

Why by September? Confused by that post. Sorry to venture off topic (again).

 

Light Weight Flywheels DO NOT reduce torque they only reduce INERTIA the reason it is harder to get moving from rest with one is they have a LOT LESSS INERTIA stored in the flywheel and so require more starting torque from the engine.

 

Inertia... torque... point taken but just tring to expalin it... When it get to the wheels it is the same thing though and reads a torque.

 

"...should have full boost by 4.5K rpms - to me that's waiting around for too long"

since u value low end delivery, and have PFC, try seq'l 1st. running 12-14 psi, it's important to lower transition about 500 rpm. check PFC tuner/board for settings. can always do the simple ns/rikki mod later, but that meineke cat might have to go.

 

maxpesce- When you have a loss of inertia what does that translate as on a rw dyno?

 

it depends on exhaust and intake restrictions

the flywheel doesnt hame much to do with boost. it will just let you build more boost by virtual of spending more time in the gear.

 

Sorry about getting so off topic on my post.

As for the September remark, getting your hands on a gt 3540 in less than a months time isn't easy from what I've heard. They are becoming very popular and are somewhat new. September was just a guess. No, I wasn't quoted that by anyone. Once I've got the cash and the rest of the mods done first, I will hunt one down.

Once again, sorry to get off topic!

 

Jesse (sorry if I'm butting in here Max...),
It depends if its an inertial dyno or not . "Dynojets" and most dynos here in the states are inertial, I'm not sure what you guys use over in Japan though, based on vids it looks like you use mostly inertial too. Inertial dynos work by measuring how quickly the engine can spin up the wheels to a certain speed at a certain load and measure power/torque that way. In this case, a lightened flywheel, as well as lightweight wheels and other lightened drivetrain parts will show as an increase in horsepower. However on a brake dyno, which works by loading up the engine until it can't accelerate anymore, you'll see no differences because there's no change in inertia. FWIW, a brake dyno is a true measure of horsepower, although I personally think an inertial dyno gives you a better idea of how much power you putting down to the wheels because most of the time when you really need the power its because you want to change your "inertia" (ie accelerate) versus needing to climb up the worlds steepest hill. Its easier to get going with a heavier flywheel because when you rev up the engine, the flywheel can store more energy and then transfer it to the wheels when you engage the clutch, so the engine will resist bogging down. However the flipside is it has a harder time spinning up too, so both ways its a tradeoff.

 

4500 rpms is a LONG time....long enuff for me to get a good jump on you....i just raced a sweet rex running non seq and he spent a lot of time trying to recover lost ground.

if you are running stock twins..which im assuming that rikki is...then youll get it by 3650 as he states....but if you have larger wheels and shafts and all the other goodies then youre gonna be waiting around...no way would i run non seq on that car with a streetport...yikes...if you want lag like that you should have gone with a t78 and had some real fun.


i debated the same thing with the m2 set...but im so happy with the low end torque "regains" after the loss of torque caused by my streetport..that Im smiling all the way around town.


honestly though..ill ask ya again...if you were going to wait for full boost at 4500 why not just go with a big big single?


jason

 

This has turned into a GT3540/lightened flywheel debate - if I wanted this I would have done a search As earlier stated, a flywheel's(lightened) only downfall is started from a dead stop - if requires a little more gas and clutch feathering but once you're going (especially in 1st and 2nd gear) it rips - who cares about the GT3540...I am a town driver and race occasionally - I don't go to the track or autocross events. I like driving backroads and a couple of highway blasts to 130 once in a while. Right now I have the full conversion of non-seq with all the hoses and solenoids out. But I have a problem with my primary turbo right now (it's not spinning at idle at all) so it's either a carbon seal or a bearing. Lag is pretty bad because of this. Sequential does put more stress on the shaft and I'm planning on getting tuned for 15 psi - the BNR hybrids use the stock snails but upgraded compressor wheels machined down to about the same weight as the stock FDs wheels. but the compressor wheels he uses are much more aggressive than stock. Should be good for about 30-50 rwhp over stock turbos - just have to wait until Aug 13th to dyno and see. Need more input on running upgrades sequentially or NS here guys!!!!!! Somebody has to have some experience with this.

 

you didnt answer my question and seem to have answered your own.

4500 is a long friggen time to wait for 30hp gains.

you lose a lot more than that down low.

you said you want it as a daily driver and not a race track car...well your answer is there already.

if you want to wait for that kind of lag then you should have gone big single.

go seq and try it out..its not a huge pain to go non seq if you decide you like it.

there isnt a lot of guys running your turbos...no one around to give you the input you need i assume...same as i found out with the m2 set.

even with the m2 set i had the same question..do i go non seq...well after a long conversation with brett at m2 what it came down to was the question "what is the point of going for low end power gains with the m2 set if im only going to nullify it by going non seq?"

i went seq.....and am very happy. if our sets are as similar in size as i imagine then I know you will be happy too. my biggest smile comes from having boost on the street immediately...i know the bnrs will be a bit laggier than the m2 set but they will still be a lot of fun Im sure.

dont get greedy....get your car going strong seq and if you still itch for more kick high up then go with the non seq

 

ps...do you have bad seals on those bnr's already? or is that your old set?

j