danmc77

Ok guys, I know you've covered this many times so I did use the search. But I couldn't find an exact answer to my question:

What exactly is the advantage of going non-sequential with the stock turbos? Is it only to eliminate vaccuum lines and chambers, or is there a significant performance increase?

I will be using a new/reman engine with stock turbos. I've read alot of threads on "how to", so I just want to know what advantages of both the "poor man" and "true" non-sequential conversion. Thanks!

rotoboy661

Search

DaleClark

iTrader: (55)

The primary advantage is simplicity and removal of the boost spike. Some guys with very modified cars have had VERY violent transitions to the second turbo - like a 100hp jump when the second turbo comes online. In some situations, namely road racing, this can result in big problems if you hit the second turbo in a corner.

You really need a fully-opened system to run non-sequential well - intake and full exhaust.

But, you do lose a lot of low-end response and grunt going sequential.

Personally, I don't recommend it unless you're in a situation where you need it. Yes, the sequential control system is complicated, but when it works, it works great.

Dale

cewrx7r1

iTrader: (2)

Only for poorly converted non-seq, or with basically stock engines with non-seq.


Ask anyone with a properly setup non-seq or single tubo and most likely they will laugh at you as they live you in their dust. You want low-end torque, buy a V8 truck.

JONSKI

How do you poorly convert to non-seq?

RX7Wishing

The poor-mans non-seq


My mods are listed in my sig. And im thinking of going non-seq.. During transition i spike to 14 PSI on cold days.

rynberg

Get a boost controller, problem solved.

I really feel the need to address the boost spike on the track crap that always gets brought up -- first of all, almost no one tracks their car. Secondly, once you cross the transition on the track, you are essentially running non-sequential the entire time -- at least with the PFC.

Advantages of non-seq:

*smoother powerband
*more reliable and consistent boost

Disadvantages of non-seq:

*increased lag time and loss of power below 3-3.5k rpm

Don't tell us you searched, there have been dozens of threads on this and they all say much the same thing...

danmc77

Thanks for the help guys. I did search. I spent the last two days reading old threads and checking out links. Most of them are people arguing with each other. Some links with great info about how to do it, but I didn't find one that explained exactly what the advantages were other than simplifying the vaccuum system. Whatever, I'll keep looking.

danmc77

I looked through some of the similar threads and found my answer. I'm going to stay with the sequential due to lack of low end power. I've worked on my twins for the last few years and feel comfortable with them. I changed them to silicone two years ago and haven't had any problems. I don't feel the need for simplification of the VL's at this point.

DaleClark

iTrader: (55)

Problem is, a LOT of the documentation on the RX-7 has been written by hardcore track guys, especially a lot of the stuff on Steve Cirian's site. This gives the feeling that their experiences/stuff that broke is "normal", when the car in actuality is under very heavy stress.

Granted, it's been AGES since I drove a non-sequential car. But, Carlos Iglesias, who's a good buddy of mine and who pioneered the non-sequential setup, told me he always remarked at the difference in low-end power when driving a stock or near-stock FD.

Regardless, I think that 10% of the guys who have gone non-sequential did so for a good reason, and the other 90% did it either because they wouldn't put the time in to troubleshoot a problem with the stock twins or they thought that "ripping out all that crap" was cool.

My old 10th Anniversary FC with a big turbo gave me a lot of experience in driving big-turbo cars. The lack of low-end power really isn't that bad, when you consider it can rip to redline RIDICULOUSLY fast. But, I have had experiences in certain gears and speeds where I felt I was waiting for the boost to kick in. Again, not really an issue at the drag strip or track, when you're constantly in the powerband, but more of an around the town on the street kind of issue.

Dale

blueskaterboy

if your not getting a single, do it, and get a profec or apexi, with a manual controller, it will be very laggy. also having a nice exhaust setup, like no cat, will help.

also in traffic, not having much boost under 3k is a plus. i've ridden in seq twin cars, id rather have my nonseq (which i do hate and want a single, TOO WEAK!)

rynberg

Care to explain how? It's a hell of a lot safer and more fun to have instant throttle response and power anywhere above 2k rpm to me....

kale717

exactly

jimlab

That's the first time I've heard Carlos' name associated with pioneering non-sequential.

As far as I know, Kevin Wyum was non-sequential before anyone else and he helped with or advised Todd Serrotta in converting his R1, which Trev Dagley then bought. I met Trev in early '97, and at that time, his dad's CYM R1 was already converted. I converted my car shortly after getting a ride in the CYM, in mid '97. Where does Carlos fit in all of that? I don't remember Carlos showing up until a bit later.

1QWIK7

iTrader: (33)

maybe he meant in rush hour traffic? save gas LOL

akiratdk

I have a nonsequential setup and I have yet to have problems.... I think the reason many of us go this route is because since our rats nest hoses are getting so damn old and stuff the sequential setup becomes unstable....therefor they go non-sequential to remove any turbo problems plus a smoother powerband....
and YES there is no lowend power at all!!!~~ my boost kicks in at like 3000 - 3500!!!
not much for a daily driver.....damn...

jimlab

Let me guess... you still have your catalytic converter(s)?

rescueranger

iTrader: (15)

dunno how realistic this is but check out initial d 4th stage .. episode 8 .. features two fd3s racing against each other .. one single and one twin .. heres a spoiler .. the rx7 wins

RotorJoe

Well of course, we know the 7 can't lose

I like the non seq set up. I was ale to build full boost by about 3800rpm. I had enough torque to get around town and have not had any problems. However racing from stops lights was out of the picture. Couldn't get real traction tell I got the car moving. I however have the power bug and am going to a full single turbo when I rebuild my current "popped" motor.

To me it sounds like everybody will have a different take on the draw backs and benefits. Some people will think it takes away too much low end power, others (me included) don't mind. Others will say it simplifies things and makes it more reliable, I tend to agree, just because of the vacuum hose deletion. It is up to you.

1QWIK7

iTrader: (33)

well i love and hate my non sequential setup..

i love it when im going to work cause its really early in the morning (6am) and no one is around.. i can drive as slow as i like, hitting revs at like 2500 max.. my job is only 2.1 miles away so its a nice easy drive..

i hate it when going home from work/or going to other places where it involves alot of stop and go and alot of cars.. i have to rev the crap out of it to keep up..especially from one light to the other, otherwise cars will ride my ***..usually i rev it to like 4200 to keep up..

but on the highway? OOO MAN do i love it!!

3rd gear pulls are amazing, feels like im driving like a really fast car (LOL)..

and im only boosting 8lbs, i wonder what a single will feel like lets say at 18lbs? WOW

cewrx7r1

iTrader: (2)

From this discussion you can tell who grew up with real sports cars, and who grew up without them. Who have manual trans attitudes and who have auto trans attitudes.


If you want low end torque and want to shift less, stay sequential.

If you want the faster of the two, go non-seq.

RotorMonkey

I'm about 98% sure that this is the route I'd go. Can someone describe how the car accelerates from idle to 3-3.5K (when boost builds up)? Is it like driving a NA 4 cyl. (stepping on the gas and not going anywhere) then bam, boost comes on and you're out of there like a bat out of hell? I'm getting rebuilt next month and we are doing a full NS setup (ported wastegate la-de-dah). Is the low-end torque that bad? Aside from running a full exhaust, are there other ways to compensate for the loss of the low end grunt....OK, for those who went NS, who regrets it and who loves it?

rynberg

Chuck, I greatly respect your PFC knowledge but that post above is pure CRAP.

I have never owned an automatic. I have owned sports or sporty cars for 11 of my 14 driving years. And I prefer sequential.

Why would anyone choose a SMALLER powerband? Manufacturers try to widen the powerband with every engine revision. People like V8s because of the low-end torque. I don't see why non-seq fans villify people for ENJOYING GOOD THROTTLE RESPONSE BELOW 4K RPM. Of course, if I want hard acceleration, I'll downshift. But it's the nice torque when you are just crusing around at 2500 rpm that is enjoyable. Who wants to have to downshift and rev up to 5k rpm just to get around someone? I don't get it.

I understand when people go non-seq to achieve more controllable and consistent boost, but to say the overall driving characteristics are better is illogical.

jimlab

Maybe we don't see why people make such a BIG ******* DEAL out of a few lb-ft. of torque. It's not like a 2-rotor engine produces massive amounts of low rpm torque even when sequential.

rynberg

Again, why give up what low-end torque we have? Most of the dyno sheets I have seen show an approximate 50 lb-ft difference at 3000 rpm (200 vs 150). That's 33% more torque than a non-seq car. Hardly an insignificant amount.

I'm surprised you're such a non-seq fan given your repeated statements about how much better the low-end torque of a V8 is...