Sequential vs Non Sequential Turbos
 

First post, hopefully much more to come. Great forum. This has been VERY helpful in terms of teaching the exact oppossite of a motorhead, or "rotorhead", something about cars, FD's more specifically. I'm planning on purchasing sometime between now and November and am sucking up everything I can between now and then, cruising ebay, autotrader, yahoo, and the forums here trying to "score" a beauty for the right price.

My Question: I have been unable to find information regarding the stock turbo set up and the "non-sequential" set up. I have read that single turbo's are more powerful and don't spool up as quickly at lower RPM as the stock twins.

Can anyone offer me a bit more insight? Am I getting confused with terminology?

Thanks in advance...I scanned some forums with limited luck..If I missed it, flame away.

No Sig.

Non-seq means, the twin turbo set-up is running in parallel. they spool at the same time and achieve 10psi later in the rpm band.

You asked for it :)
 

The stock system is sequential in an effort to minimize lag......the first turbo comes online at ~3000 rpm, and some exhaust gas pressure is routed to the second turbo to "pre-spool" it. At ~4500 the second turbo comes on line. Stock boost pattern is 10 psi from 3000 to 4500, dip to 8 psi, then climb to 10 and hold until redline.

Going non-sequential, both turbos operate in parallel. You lose most of your vacuum hoses, check valves and solenoids, which will decrease the number of boost related problems that many FDs experience.

As far as lag and spool, a lot of it depends on the airflow mods done to the car. I would imagine a completely stock car run in parallel would have atrocious lag. But we had a customer's car with stock motor and stock turbos running parallel with open exhaust, intake, intercooler, power fc, and I couldn't believe it when I drove the car. Much less lag than I expected, and the car pulled like a mother once on full boost (might've been 4000 rpms, not quite sure). The car was perfectly streetable. Keep in mind that an FD spends almost none of it's life below 2500 rpms and zero below 2000. 3000 rpm is a good cruising rpm, and the car is geared towards it.

My R1 has BNR Stage 3 twins----upgraded stock twins with different compressor wheels and dynamic seals to aid in spool. I'm running in parallel, and get full boost (17 psi) by ~3700 rpms. I have 10 psi by ~3200, and the car pulls *hard* from 3000 to 5000, at which point the car explodes and I'm fighting for traction. The car is very streetable, and most FD-owning passengers that ride with me can't believe that the turbos are non-sequential b/c the car is so responsive. I usually have to pop the hood and show them the huge space under my upper intake manifold to make them a believer :).

Great Stuff, Thanks to both.

Goodfella - Are you saying parallel turbos ismore reliable, with a bit more lag at low RPM's, that can be reduced/eliminated with the right upgrades?

Single Turbo is out of my league at this point (performance wise, not cost wise) - baby steps.

If I'm looking for a reliability mod'd, slight performance mod'd daily driver, what would be your recommendation? My goal is to have a kick in the pants, clean looking FD that is pushing enough juice to disgrace your average $35K sports car.. Also, what would be the cost associated with it (your recommendation)..ballpark? I can price out the parts, but keep in mind I'm REALLY wet behind the ears and would likely have the work professionally done due to lack of a garage and lack of tools.


Thanks again!

I still love my sequentials... that's why i bought it in the first place! it spool up really fast from 1800~~ :D but then again, i never took a ride in Goodfellas FD3s... ;)

I dont think I would ever consider non-sequential. I do get nasty boost spikes on my car that sometimes cause a fuel cut when shifting aggressively into 3rd, but I could not deal with the lag. My midpipe and ported engine make my car a total dog below 2500 as it is. I think it would be that way until 3800 now, and not fully spooled until 4500.

I'm not saying anything about non-seq until I get my car converted (yes, I am all about simplicity...plus it's a step towards the big phatt snail) I really like sequential now, but considering how far I live from a reputable rotary shop (4 hours) I would rather have simple and a little lag knowing I can easily work on my own car without getting tangled up by meters and meters of vacuum hose. So I have seq turbos now, then going to play with non-seq for about a year, then going single after....So I guess I am saying "don't knock it till ya try it!"

i haven't searched much on this, but since this thread is on the topic, can you upgrade the sequential stock turbos' that we have? i've heard of rebuilding them, but aside from upgrading the seals, what happens in the process of doing that?...

edit: also as far as going non-sequential, are there kits for 'upgrading' to go non-seq? or does it use the stock turbos?

See the RX7Store.net link at the top of this page...You can convert the stock turbos to non seq...However, you can alos have the stock turbos rebuilt by BNR or Bi State Customs and have something like the following done.


These upgraded stock turbos allow you to run a much higher level boost than stock..I believe the stage 3 BNR turbos peak at about 17psi but I have head them being run at up to 19psi...

awesome info..thanks

I converted to Non-Seq. because I was having too many boost issues and I was noob who didn't know how to trouble shoot the Seq. System. I was also pretty lazy.

Non-Seq is fine for me. I get max boost(14psi) by 3800 rpm.

Don't convert to Non-Seq if your Seq. system is running fine.

I prefer the non-sequential setup. It hits harder I think, just feels better to me. Less to worry about too.

GoodFellas first post here is good. But I'd like to add:

The stock seq system is awesome, when it works. The problem is, the cars are 10 years old, and there are 120+ feet of vacuum hose, and 30+ solenoids that control the stock system. Something is bound to break. And even if you get it fixed, and it works, again, everything in there is still 10 years old, and will break eventually.

The non-seq system on the other hand, does not spool quite as fast, but yields the same power in the end. It is more reliable, because there is more like 20 feet of hose, and under 10 solenoids, so there is less to break. For me, I want reliable boost every time I hit the gas.

As far as late spool up time, if I'm seriously driving the car, the revs are never below 3-4k anyway, and thats where full boost is achieved with a proper non-seq system, so lag is not an issue. There is little to no difference in lag in both systems if you're cruising at like 3500rpm, then hit it. Both spool very quickly.

30+ WTF??????? then under 10?????

If you go full non-seq, with no emissions, you will have 0 solenoid valves under the UIM. The only ones I can think of that you keep are for the wastegate (if you have something that can control it) and the....purge system (which has nothing to do with the turbo). I feel that NS yields a little more power, do to the lack of butterflies valves (maybe not noticeable) and less resistriction on the exhaust...NS pulls hard thru redline, where seq. would drop off...

I am speaking for my car (not so much stock).

yes, seq. is awesome when the car is stock and works perfect. CRAZY spikes and outta control feelings while the tires are breaking loose at 4500 rpms...not for me.

Sounds like you need some ported wastegates and better tires :)

what kind of price did you guys pay to re-do your stock turbos into non-sequential? did you have to buy anything in addition to upgrading to non-seq or do they just remove a lot of stuff? i guess what i don't understand is what is the process of going non-sequential? is it just a matter of adjusting the ecu or something? bah im such a newb...thanks!

-Dan

NS sucks:D - no, it is a step in the right direction if you're looking for reliable boost everytime. It pulls hard to redline with no fluctuations. I like mine set up S but to each his own

Try more like under 30 feet and there's about 5 solenoids that are involved with boost control (less if you have a boost controller). I have owned my car for 20 months, daily driven, and the only issue I have is a dip down to 5 psi at transition that happens so fast, it doesn't even register (on the butt or real dyno). The system really isn't that complicated.

If I was just worried about driving hard all the time, I would probably go non-sequential too. But I enjoy having decent low-end torque. Pounding on the gas at 2500 rpm in 1st-3rd results in a pretty damn fierce pull and makes around town driving (again, the daily driver aspect) much, much more enjoyable.

I won't argue that the non-sequential setup is more reliable with a predictable power curve.

I love my non-seq but I would most definitely not recommend it to those who are only lightly modded. You need alot of flow to make up for the extra lag. To me my non-seq seems to yield more power but like is been said before, to each his own.

Done and Done (S03's).

I was over the 300wrhp mark when I was seq.

i never had any problems such as these. Even with an open exhaust, the power FC always controlled boost.

As far as traction goes....buy a new set of tires. My car makes 340 rwhp @ 14psi and my car handles TOTALY neutral. I have toyo proxes ts-1....great tires....you have no idea what these can do. One of the best mods i have done!

will can
 

Then somebody give the web page that show me how to go non seq?

Re: will can
 

Do a search, and I'm sure you'll find a ton of hits. Try the username 'dontbearikki'