non-sequential and lag
 

I know there's a lot of posts about this, but it's hard to find clear information about the lag experienced when people go non-sequential. In older posts many people say that "if your car is heavily modded the lag should not be that bad." I'm thinking about going non-seguential b/c lately I'm having trouble building full boost (always about .06-.07 bar from where I should be), and I'm worried that more problems will just keep coming. So with my mods (in my sig), do you guys think I would have noticably bad lag if I went non-sequential?

-Matt

non-sequential tends to "lag" appx. 400 rpms. Mine normally hit 11 psi at 3200~ rpms(It's been awhile so don't quote me)

You should be fine. It pulls so much harder mid-range you wont care about the few more rpm that you have to wait.

double post deleted

I went NS because I was also having boost issues.
I did the poor man's NS conversion. I think I get more lag than most: 14 psi by 3800 rpm consistently.

Either I did something wrong in the conversion or the HIGH FLOW CAT is causing the additional lag.

Not too familier with the "poor man's" non-seq. Does this cause more lag than the "normal" non-seq mod?

Nope, it's the same. jpandes numbers are pretty much what you can expect if you look at the dynos of the NS people. I've seen many people "claim" less lag but I've never need a dyno sheet to prove it (on stock twins).

IMO, fix your boost problem. NS is not a fix, just a work-around and it doesn't guarantee that you still won't have a boost problem.

Not to frighten you away, but I don't get full boost til just over 4000 rpm. The only flow mods I have right now are the intake and downpipe, though. With your mods, I'd put you somwhere in the 37-3800 rpm range for full boost.

But really, how often do you need that much boost any lower than that? If you're racing someone, or pushing the car hard, the engine never falls below 4krpms anyway, so why worry about lag?

I say just do it, I couldn't be happier with mine, and thats with a lot more lag than most.

911gt2
i'm glad to hear your description of your boost pattern since i have the same mods and my car is responding exactly the same as yours. i never had the car working properly with it hooked up sequentially and i was considering going back to sequential just because i'm not sure what i am missing. can you think of any reasons why i should switch back in your opinion?

Why you should switch back to sequential? The only reason to switch back is for low end response. Which is really nice. I loved having 10 psi at under 3000 rpm, it felt great.

But the stock sequential system is just way too complicated IMO. There is what, 120 feet of vacuum hose, and 30 odd solenoids? Something will break eventually. It's just not worth the trouble to keep it going the right way. I've never felt it work completely correctly, because I had a secondary boost issue from when I bought the car (~7 psi, dropping off to redline). But I've been told that when it works, it's awesome.

Do a search sometime for "low secondary boost" or "sequential issues" or something like that, and see just how people have issues with the system. Not worth the trouble.

Then there is the issue of reliable boost. Every time I hit the gas I see 10 psi. No matter if I let off and hit it again, let it build slowly, don't build at all 5k rpms, then drop the hammer, it makes no difference. With sequential, wierd things happen. If you keep the car at part throttle, then hit it, sometimes you get really slow building boost, sometimes, it spikes, theres just too many wacky things to go wrong. With a full exhaust and non-seq, you can hit full boost by 3800 rpm, which is not very long to wait.

Long story short, don't go back.

Thats very true, it might not fix your boost problem. It didn't fix mine the first time around. But that was because my secondary turbo was blown. If the issue is with one of the many feet of vacuum hose, or a solenoid or actuator that controls the seq system however, it will fix it.

I thought of it as a simplification. There is a seq system simplification diagram around, and I felt this just took it one step further.

I see the non-seq as a poormans single turbo. The twins effectively function as a single in non-seq mode, but you don't have the issues of finding a turbo, manifold, new dp, intake, BOV, IC, piping, and ECU to control it all.

It is a workaround, but it's also a workaround for future boost issues that the seq system WILL have. I don't know, think of it as a reliability mod too.

Basically, I've been considering going non-sequential for a while and this boost problem just made me consider it more seriously. If I'm going to have to go through all of my vacuum hoses and solenoids etc, why not do the conversion now. I'm not necessarily looking for it to fix my problem, but diagnosing the problem may get so intensive that I might as well go ahead with the coversion. I'm still not convinced that it's what I want to do, though. If I can be convinced that I will gain some more power and not be bothered by an unreasonable lag, then I'll go for it.

People have claimed that it gives a lot more power in the mid-range (like racerfoo above). Is this simply due to no pressure drop durring the transition, or is b/c of something else?

That's opinion, not fact. I know several owners (including myself) that aside from user error, have never had a problem with the sequential system.

The only problem I've ever had was my own mis-routing of two lines to the UIM when I was fixing another problem. I can't complain much as that was the first time I ever removed and reinstalled the UIM myself and I should have checked with the vacuum diagram first.

So, that makes almost 7 years of ownership without problems. Take a look at a dyno chart, you only loose with the poor-man's NS compared to the standard sequential setup. You do gain with the full-NS in the higher rpms as you have slightly better flow. So if that's what you need, that mod with worth wild.

IMO, doing NS with the twins is a waste. If you want a single turbo, get one. Basically, you are getting the lag of a single and keeping the heat of the twins. A loose-loose situation if you ask me.

Yes, you don't gain more power you just have a different power curve (with the poor-man's NS).

same here....don't get full boost till like 3600-3800 rpm..... it was worse before i dropped the efini y pipe. i am full non-seq. it lags but not too bad....14 psi by 3800. k

And I know several thousand that have had issues. Taken a course in statistics lately? Numbers are not in your favor.

I called the non-seq twins "poormans single" for a reason. It'd cost upwards of $5k to get a properly functioning single, with all of the hardware and software needed to do it. It cost me about $5 to do the poormans non-seq. It's a taste of single without all the work and money. You call it a loose-loose situation, I call it a win win. Cheap, yet effective. To each his own!:)

I'm no statistician either, but I know that people who are content tend to tell one person about it, people who are not content tend to tell 9 people about it. So you may find that your analysis is off because you have mostly heard the negatives. I have had three FD's over the past 8 years and never had an issue with sequential. Care and precaution seems to do the trick for me.

I get 17 lbs by 4000 on bnr stage 2s...I hate it. I have the full non seq. Worst thing I ever did! Stay seq! If I'm just cruising around town...my car is not quick..its a dog. Its either a dog or a missile, there's no middle ground.

mcf has it right. This is a trouble-shooting and technical forum. Of course you'll only read about people having problems as they will be asking here for help. Why would they post if they didn't have problems?

That's like going to a support forum for a product, and then not wanting to get the product because there are people in a "support forum" with problem. :rolleyes:

However, as mcf said, "care" is #1. The sequential system typically fails because of vacuum or solenoid problems which can be remedied by going non-full NS. Both problems are typically caused by heat from the underhood temperature. Any other problems usually will carry over to NS.

With proper care (and proper work done to the car), there shouldn't be problems at all with the sequential system. Do it right the first time so it doesn't need to be done again basically. So, if your headlights go out, are you just going to remove them instead of fixing them? ;)

Going NS to fix a boost problem is the wrong reason, IMO.

I don't understand any of these replys. 15lbs by 3600 & 17lbs by 4000rpms ...what's wrong with that? If transition takes place at 4500rpms, that means in sequential you are at 10lbs at 4500 on a stock 7. I was at 15lbs at 4500 (modified) sequentail. How many lbs are you boosting at 2800 vs at 3000?

If you can describe parallel as slingshoty then I can understand the drawback because that is not streetable to me. As far as loosing 400 low end rpm, that will happen with a single. Basicaly you are tading low rpm for reliability (same as single).

If both turbos are online then aren't you hitting full boost in parallel sooner then you would in sequential waiting for the transition?

Doesn't parallel change the power curve from high end to midrange, which is where all the power in a "non" ported engine is anyhow?

To answer all of your questions:
The difference between hitting 15 lbs by 3600 rpm, and 17 by 4000, is entirely dependent on flow mods. With a full exhaust (dp, mp, cat back) the turbos will spool a lot quicker. The guy who hit 17 by 4000 had a few less flow mods (say, a high flow rather than a MP) than the other guy. The twins function as a single when in non-seq mode, so they both need to spool up together, which takes longer.

Non-seq is far from slingshotty. I experience a "boost building" sensation, which basically involves a growing smile on my face as the gauge climbs to 10 psi. Even with a full exhaust, power is far from instant in non-seq mode, and it is more than streetable.

With both turbos online, as I described above, it takes longer to spool them up, so no, you're not getting full boost before you would when the were seq. In seq mode I got full boost at about 3krpms, then I should have had re-full boost after transition. The idea behind sequential is that you have one turbo thats small, easy to spool, but has a low flow capacity. The second turbo needs much more exhaust to get it spinning, but has a much higher flow capacity. So the first one comes on very low in the rpm range, but loses it effectiveness somewhere around 4500rpm. So the second one is calibrated to spin enough at 4500 rpm to achieve 10 psi, and it can create that just about til redline. The faster the engine spins, the more air/unit of time it needs, so the turbo with higher flow capacity comes on later in the rpm range.

Non-seq makes them both spin all the time. So they take longer to spool, but you don't have the transition period in between, but you have to wait longer for both to get going.

Non-seq moves the power curve, but not to lower rpm range, it squishes it up into higher rpm range. Because it takes longer to hit full boost, the power curve moves up.

Let's let the number do the talking.

https://www.rx7club.com/forum/showth...hreadid=212547

Trying non-seq with most bolt ons, I found very good response going wot at 3500 rpm or above .. not doggish. But that is not likely at 3k or below. With seq'l, I hit 10 psi at 2400 rpm in 3rd ... valued by some like me.

Mid range with simple non-seq is better due to lack of transition near the torque peak.

non-seq is inherently rmore reliable by simplicity, and results in less manifold thermal cracks due to more uniform heating.

Exactly. Even getting boost at 3800 rpms NS verse sequential at less than 2400 is a huge difference. The numbers don't look so far of at a low range, but over 1000 rpm difference is more than enough for me. I'd rather not get beat off the line by a Neon. ;)

As I said, the poor-man's NS mod is great if all you want is top end power. But switching to it because of a boost problem is the wrong reason IMO.

However, saying that it's eventually going to fail is like saying your tires will eventually need to be replaced. It's a mechanical system that like anything else in the world, can break. That doesn't mean it's worthless.

I have never been beaten by a Neon. I have also not been beaten by my brothers 2003 WRX. Nor have I have I been beaten by my friends modded 91 DSM (15 psi). Both of those cars have a little something called AWD, which happens to give them an advantage out of the hole. (Ok, so I lost off the line, but caught up really quickly) Keep in mind my car runs stock boost levels, and has very few power mods.

I don't consider 4k rpms "top end." That is actually dead in the middle of the rev range. And thats when I get FULL boost. it builds from about 3500rpms or so. And it'll spool much quicker with the rest of the exhaust.

I understand that all things mechanical break at some point, but why not replace the broken piece with one less likely to fail? When your stock tires popped, did you replace them with factory rubber? Or did you get Z-rated tires with a 3 yr/50,000 mile warranty?

Did you bypass your AST? Same type of thing. Some might argue that it's there for a reason. Other see it as a fault in the stock cooling system, and get rid of it.

My point is, take two cars, on seq, and one non-seq. Full exhaust on each, and take them to a track. They'll run dead even in the quarter, and dead even on a road course. Why? When a car is being pushed, it's never below 4k rpms anyway, so why have the power available there, while walking on thin ice with reliability? Do you ever race anyone from under 4k rpms (aside from the launch)?

"Its either a dog or a missile, there's no middle ground..." Widebody

Man I love the missle part about it! hehe

Bryan
www.bnrsupercars.com

Feared7 - Maybe you can explain it better. These replies are not consistant and are confusing. Full boost to me is the max' boost you can do, not when the turbos "begin" to boost.

On sequential you can have full boost by 4500rpm, but that's only "1" turbo. So if on parallel you have full boost by 4500rpm's on "both" turbos, isn't that more power?

Even at 4000 rpms, the only thing you won't have is the transition. Any FD with modest mods makes the transition almost non-existant. Hell, just about everyone that drives my car never even notices the transistion.

Nope, I upgraded them. I didn't rip them off the car never to put them back. :p:

Nope, didn't get rid of it.

Race? 90% of the people on this forum don't "race" their cars. The most racing over half the forum does is the typical street light race. I will be doing open track racing starting next month (providing everything is in working order).

However, I beg the differ on the 1/4 mile part though using exact same cars (on stock turbos). Since you aren't gaining anything in the top end only losing the low, the poor-mans NS will not yield the same results there. The full-NS should help as you'll gain slightly better airflow and some added power at the high end.

You are missing my point. I never said that noone should ever do the poor-mans NS. What I said was it's not a good way to fix a boost problem and it doesn't guarantee that it will fix the problem at all. Troubleshoot the problem, don't bandaide it.

If I could "easily" trouble shoot my Seq. system, I'd go back in a heart beat! 90% of my driving is in the city. But, I know that it isn't going to be easy. So, I probably won't be spending the time to chase down all the issues. Besides, my mechanic said that I have some cracks in turbos and that I may have some transition issues.

I'd suggest using the Sequential/ Non-sequential switch. It's all done electronically. Takes about 45 minutes to install and you can decide on the fly which one you like for a certain situation. I installed mine on a perfectly working simplified turbo control system. If yours isn't already working it'll probably still have issues until u fix whatever is wrong.But if you want to try it I know there's info on it somewhere on this forum. I think i even linked to the install instructions once. Just make sure you get the correct switch. It's not something u can just pick up at Radio Shack but it's not expensive. If u do want to try that route and can't find the info let me know and i'll try to dig it up.

I know I've already explained and you probably don't wanna hear from me again, but I'll try again anyway.

Full boost is full boost. In stock form, 10 psi is it. Whether you get it at 3000 or 7500 rpm, it's still 10 psi. There is more power later in the rev range, but only due to the fact that the engine is spinning faster. The number of turbos operating has nothing to do with it, it all depends on what that little gauge on your a-pillar says.

Yeah but I like arguing :D Sorry if you have better things to do, but as for me, I have no life outside of my car (especially when it rains 24/7 and I can't go play with it :( )

911GT2,

You can't really argue with someone unless you are debating the same point. Your poll misses Mahjik's point by a few hundred yards. A few hours of preventive maintenance on the rat's nest and somewhere between $100 and $300 on new parts (hose and solenoids) will provide years of trouble-free driving with the sequential turbos. Substantially changing the characteristics of the car for a fews hours of work is not a good enough reason to go to NS.

Good point for 100% racing use, but for mixed use or non-race use, seq'l has it's place.

I like the simplicity of non-seq, but I hate the response. It is true that when I'm rowing through the gears at WOT, it doesn't matter whether I have sequential or non-seq.

But for the other 95% of the time I'm driving, I'm glad my car is sequential. My car makes about 15 psi almost instantly, even as low as 2500 RPM. This is great when I'm driving in the city, or coming home from work on curvy mountain roads.

I think non-seq would be a BIG mistake for someone who autocrosses. Keep that in mind if you are an avid autocrosser.

BTW, I have had no problems with my sequential setup since I simplified it a couple of years ago. A few feet of hose, and only 6 solenoids. The emissions system is more complicated than the sequential system, don't confuse or combine the two.

Wade

Ok then, obviously I have become the minority here. And now to bow out with what little dignity I have left, you guys can keep your seq, and I'll keep my non-seq, and we'll all be happy. :)

Well I had just done a hose job in Jan and replaced a lot of the solinoids, which amounted to $400 and no car for a few weeks. Then I start getting boost problems AGAIN a few months later. Rather than spend more money, time, blood, and sweat trying to figure this out again, when I know i'm going to dump it when I go single in the future, I just trashed the system. I'm full non-sequential now. I start building boost at the same time I did before, but it rises a little slower now. I think the only people who would complain with this set-up are people who have been spoiled by the almost instant boost of the SEQ set-up for too long. If you've ever driven any high powered turbo cars you would know that full boost by 3500 is not bad lag. Especially when you can rev out to 8000-9000rpms, thats a very broad range of power. And what is the problem with downshifting if you need more power? Below 3000rpm should be for cruising or light acceleration. If you need to get on it, downshift for gods sake. That what gears are for lol.

For the simplicity, reliabilty, and smoothness of this setup, I'd say its easily worth the few hundred rpm of boost I lost out of 8000.

My mods are listed below, so my results will probably be alot different than yours. Good luck with whatever you choose.

With seq system I can hit 7-8 psi at 1800rpm, full boost is just a couple hundred rpm later. I can imagine myself smoking the non-seq cars in most daily driving situations. For auto-xing non-seq is not a good choice in any situation. For road racing I can see it working. For in town/city driving non-seq will also loose. Where do you drive your car?


Although the rotary doesn't mind being revved up there is NO reason it needs to be cruised around at 3500-4000rpm all the time. So non-seq guys are either buzzing around at an uncomfortable rpm or completely out of the powerband most of the time.

I haven't had any problems with seq systems breaking myself and I've had 13 FDs. The problems I've had with boost was a non functional double throttle control and a couple cars with new motors where I had reversed a vacuum line. Both were relatively quick fixes.

Oh and what are the ages of most the non-seq guys? I'd bet on the younger side. Just because it is a "MOD" doesn't imply that it is a good one.

Cast one more vote for NS.

I've got one question. How much simplification (emmissions and other solenoids) can be done while still seuquential?

The main atractant of NS is the simplification to near nothing.

i did the full NS conversion and i get my full stock boost by 3100rpm.

-Zach

Thats awesome, do you have a dyno sheet to back that up?

Turbojeff, you and I both know that I respect and revere you as a god ( :worship: ) But I gotta disagree with you here man. As much as I'd like to see the stock seq system work flawlessly, every time, the fact of the matter is it doesn't. And until it does, I'm sticking with reliability over low range, not gonna use it power. If I wanted a wider power band I'd be driving a Z-28, SS, mustang, vette, viper, something along those lines. Half the rev range of "oh my god" acceleration is good enough for me. (Still :worship: ing though :) )

i really wish i did.....havent had shit for time lately to throw it back on. Im also waiting for another group of ppl to go back...id much rather pay $30 than $75. :)

No problem with you disagreeing with me. Wide powerbands are relative, a wide powerband on a turbo rotary is still different than a wide powerband of a V8.

Everyone is going to have different experiences, if you like what you have that is fine with me.

Still I've got some good experiences with the seq system. For auto-xing it is a must, can't really argue with that.

BTW, last auto-x I was at there was a 911GT2, he got last place in ASP, musta had a bad couple of days. SWEET car though. I'd take it and last place:).

I've had the experience to have both stock turbos and upgraded twins setup in both seq and non-seq and overall seq is much more enjoyable. You guys who say about being how when you're racing you're never below 4K rpms anyway - do you race your car 100% of the time? When you're cruising around town or on mountain roads - NS blows - again, it blows. I had full NS with both the stockers and BNRs and I hated it. There was definitely more midrange..I won't argue that. But on the street, a properly maintained and tuned seq car will be the funnest car to drive. I had my FD for 5 years and never had a problem with the seq system - I am one of the few that swtiched back from full NS to seq and loved every second of it. To each his own - I liked 15 psi by 2800 rpms..even if it was on one turbo

Thats awesome, I've yet to see one. I wanna race on just so it can hand me my ass, and I can say "I got beat by a 911GT2!"

kwikrx7, no I don't race my car 100% of the time, nor 50% of the time. Most of my time spent driving is just going to work, school, or other errand-type things. But the car is very enjoyable to me then. I can drive it slow if I want, and fast if I want. But I don't hold on for dear life at half throttle in 1st gear, as I sometimes had to when I was seq. I kinda like having the option of driving with or without boost.

There are many times I drive my car where I never even touch the boost. City and highway driving, it's quite possible to not even bother. Maybe it's just me, but I like the option.

sorry doods...non seq is a drag in town...some of you non seq guys live out in the sticks and so non seq is all fine and dandy...but live in the city and your opinion would be different if you had the pleasure of a highway once a week at most...i mean hell..with non seq you dont get to enjoy it til yer speeding...which you can do out in the country....with seq i can still play in town...zoom zoom.

911gt ...i would like to compare your dyno sheet to my dyno sheet from 4k rpms and below. i imagine ive got at least a 50lb of torque gain on you by 2700-3krpms...if you were sequential we would be much muich closer in the rpm range that is normal for daily driving.

but to each their own....tis an endless discussion.


j

I live in Worcester. It's the 2nd largest city in Mass. Right behind that little town called Boston.

Where's the info on this? Sounds neat. I'd like to try it. Can't find anything though.

The website that used to have it is down but i'll try to see if i ever saved the info on my hard drive. Gene Felber is the guy's name that had the writeup. He's on this forum and actually helped me make sure i set it up correctly. The only thing weird about it is that if i leave it in non-seq mode and turn the car off when i restart it goes into limp mode. I haven't spoken to Gene about this yet since it's a minor annoyance.