This has been great to read, not because I've learned anything, but how everyone suggest reasons to support their view and in some parts, y'all aren't even comparing the same things when you decide the other's wrong.
The problem is in communication, if each of you were to clearly state what you know to be the case, you'd see you're both right.
Non sequential uses the same turbos spinning at the same rpm after the normal transition point. So say from 5k to your shifting, the point is mute. The cars are the same. (As Kevin pointed out, this isn't necessarily true, possibly because of the wastegate being 100% open throughout) So now look at your power curve from 2k-5k and compare the two power and torque curves. Brian's point of area under the curves should be the main focus when comparing non sequential to sequential. When you are drag racing, street racing, road racing, nothing else matters except total area under the curve IN THE RPM BAND YOU ARE USING (very important to consider what you use your car for). When you are going for acceration up to redline and shifting, you don't ever drop down to below 3500... Now we have narrowed our point of interest to being the area under the power and torque curves in the 3800-~5000 rpm range. Here is where it is obvious that there is a large advantage in the non sequential setup. The turbos are both at full boost way before the sequential and therefore have more power over a longer time, therefore, acceleration is greater. Unfortunately, I understand there are some people who probably read these posts and think that max power is what matters for how 'fast' their car is. (In fact, I race a Formula Continental and have people ask me constantly how fast it is. Of course they want to hear of top speed, but I tell them around 2.3gs...) The more area you have under the overall hp and torque curves, the better acceleration you are going to have, which explains Ryan's 1/4 mile times AND trap speeds improving.
Since the topic the thread starter brought up was disadvantages to non sequential, let me offer my thoughts. After converting to non sequential recently, I think that the only part I miss is being able to ride next to a loud honda on the street and go from 30-50 and be two car lengths ahead in the same gear and back off. The car is noticably louder as you now have an open wastegate and are trying to spool up two turbos, so more exhaust is exiting the car in a more direct route. I believe that the power curve is higher throughout, but not on max hp, so acceleration through the gears is quicker, but from a poorly selected gear, expect hondas laugh at you from 30-50. The non sequential setup is great for roadracing as well, because the power goes down smooth and allows you time to adjust to the increase in power, instead of the turbos dropping boost for transition (scary with weight transfer off the already low grip rear wheels), and then coming back with more power to make sure they loose grip. The only reason I would stay sequential is if I were planning on running autocrosses where you have to sometimes dig out of very low speed corners at low rpm. The disadvantages will vary depending on the car's primary application, so you can't have an across the board answer. I use my car for high speed corners and acceleration and would not switch back to sequential because it is obvious that the car is faster now than with sequential. Wade and Ryan are both right, but you need to focus on where the power is being increased.

 

I agree, the porting is the best explanation for the increased power.

Quote:

My point is not to argue which is better (since "better" will depend on your likes and dislikes) but give people as much info as possible so they can make the best decision for their situation.
-Brian

I agree, the intended use of the car must be considered. I would never recommend non-seq for a car that is autocrossed or driven mostly on the street. For a drag only or mostly track driven car, non-seq might make more sense.

The ONLY thing I'm trying to communicate is Ryan is using his 4 mph gain in the 1/4 to try to convince others to switch to non-seq. He is suggesting it creates more power, and offers that as proof. This is absolutely false, it is undeniable, and I'm getting pretty tired of offering proof of this.

Also, when driving on a track, non-seq isn't really necessary. Once you pass 4500 RPM, the car will stay in twin mode anyway unless you drop below about 3000 RPM if I remember correctly. So after your initial trip out of the pits, you're basically running in non sequential mode anyway. So even for track people, non-sequential doesn't make as much sense as it seems at face value.

No one can argue any of the following facts:

1) Sequential and "wired" non-seq make the SAME POWER once transition has occured, all else being equal. Easily demonstrated on a dyno, totally undeniable.

2) While taking the fastest possible trip down the 1/4, the ONLY time sequential will be in single mode is up to 4500 RPM in FIRST GEAR - the rest of the 1/4 mile will be idential to non-sequential, both turbos will be online.

3) MPH is very dependent on horsepower and weight, and not nearly as dependent on quality of launch (assuming it is reasonable). All else being equal, a 4 mph gain on Ryan's car would indicate a pretty large improvement in horsepower in the upper RPM range. And this is what most people would assume.

4) Ryan's ran 4 mph faster, and non-sequential does not offer the extra power required to do so. The difference in the 113mph and 117mph runs was clearly a result of SOMETHING ELSE.

5) If Ryan MUST tell people that non-sequential is responsible for 4 mph more in the 1/4 with his car, the honest thing to do would be to offer that it wasn't because of a power increase. It must have been caused by him bogging the car with sequential, or spinning the tires too much, or offer some other explanation instead of misleading the readers.

I'm not trying to argue which is best, my point is simply that Ryan is misleading others by telling them he picked up 4 mph and suggesting that a power increase from non-seq is the reason.

Kevin, Brian, am I way off base here, or should I encourage Ryan to propagate ****?

Wade

 

Ryan,

Let me make a few things clear. I don't doubt your experience, I'm not suggesting you are lying about your times/mph. I just know that non-seq wasn't responsible, you haven't come to that conclusion yet.

Secondly, I can't get into a pissing match over which is better, because I understand there are advantages to both. People are happy with both types of twin setups. It's a personal preference.

Wade

 

I think Ryans times were largely due to the fact... Launching with both turbos, lessend his 60 ft. times.

1/10 off your 60ft. Means 2/10 off you e.t.
Drag racing is all about getting out of the hole.
So Non-sqeqential has a definite advantage in 1st. gear.

j.

 

In describing the comparo, you listed your boost as 12.3 psi, less than Brad's self titled at 12 psi (aft trans).

It may well be in some cases 11 psi up to 4500 rpm may be a limit, especially with very efficient mod package. But that was not the case in the 2 examples presented, especially Brad's, where primary boost was clearly being regulated. In your old sequential dyno run, u had a 50+ hp kick across transition, which would be a handful on a road track.

Most people are after max power, and have not tried to achieve a flat torque curve thru transition. It is understandably difficult, if u study the oem boost control logic, which takes a step change at transition.

The PFC helps hit this goal, in that the transition can be lowered. One guy did this, and had a near flat torque curve across the transition ..... very linear hp curve would be very road track friendly. 12 psi I think, mabe a psi more before a transition reduced to about 4K rpm.

I am not anti-ns, it has many benefits. My Point is the "5K and below" comparo is misleading. It states all 3 runs were about 12 psi, but used 2 seq cases where 12 psi only happened after 4500-5000 psi. This site is often linked for this "12 psi sub 5k comparo", and it's misleading. One could say these are curves where boost after transition are near equal, but sequentials had lower boost before transition, as often occurs with typical boost control approaches.

 

ok, take 2 stock rx7s, make 1 non-seq leav the other 1 the same. the can have the same reaction time but the non-seq will be making full hp before the seq because the seq has not kicked into non-seq yet! that gives the non seq way better acceleration and how many feet lead. as soon as the seq kicks into non-seq then it will hold its own and the non-seq will not be able to run away any more. there for explaining why ryan had a extra 4 mph and a better time. now if that dose not make sence i think you guys are hopeless (just kidding)

 

Non-Sequentials dont make more power?

How two compressor wheels of equal size making boost at the same time vs only one of them at a time HOW THE HELL DOES THAT NOT MAKE MORE POWER. Maybe one of you nay sayers can mathmaticly explain that to me.

Sequential Low End Power: If you release you clutch before 3000 rpms and expect performance you should hav bought a V8 mustang... If you want high rpm mustang *** woopingness you should then be allowed to have a RX-7.

Also why are some of you even bring stock FD's into this argument... If you have a stock cat AND PLAN ON KEEPING IT go post on a thread about where you can get TYPE R cup holders. Not that stock FD's dont have its place but they sould not be involed in this discusion. If your car is somehow made it trough all these years completely stock leave it that way if you want to just drive it to work... You should atleast have an aftermarket exhaust for the non seq to help spool them.

 

Quite a raging debate indeed...

...either way, If anything going non-sequential(true non-sequential) helps get rid of the rats nest underneath the UIM. My car is SO simple right now. I barely have ANY vacuum hoses to worry about, and I can get to most of them easily.

 

Coco's level 10 eh? I had one of those a while back and it had me craping flames!!! You are a pimp if you would do it again.

My self I have conqured the 1300 grams of rice and Curry in under 20 several times... But level 10 you can keep.

 

Oh I am still waiting for someone to PLEASE mathmatically show me how sequentials can possibly produce even somewhat of an equal power curve to the non... I have a feeling I will just have to wait... If not I will probobly get a good laugh and get to give a math lesson!

"Non sequential doest produce more power" HA

 

I have my red bold font ready for when u do.

 

 

From this statement it appears You do not understand that in BOTH cases (Seq. & NonSeq.) above 4500rpm at WOT
BOTH TURBOS are Producing FULL BOOST!

 

Oh I under stand that perfectly, but non reaches full boost and holds it as the sequentials are just starting to come on line as a pair, and with out a secondary turbine about to catch fire, and in a race that means the non is winning BECAUSE OF THE POWER CURVE...CURVE! (Mr Big text guy)

To make sure we are on the same page... In a race aplication (which is why we even bother to modify our cars) the non has more power at the times that it needs it most through the rpm band, not to mention removing several pounds from the engine compartment. If you race at 3000 rpms and below then sure sequnetial all the way baby!

To the wheels at an RPM that is used in street or track race enviroment, in no way does the sequential power curve compare.

 

It doesn't look like it

quote:
--------------------------------------------------------------------------------
Originally posted by laujesse2
How two compressor wheels of equal size making boost at the same time vs only one of them at a time HOW THE HELL DOES THAT NOT MAKE MORE POWER. Maybe one of you nay sayers can mathmaticly explain that to me....
--------------------------------------------------------------------------------

You are contradicting yourself.

 

With non-seq on a pretty modded car (who's Rx7 is not modded nowaday), don't you get full boost before 5K rpm? If that's true, and I think it's true, don't that mean the car will run stronger EARLIER in the RPM?

Of course, at the end, higher RPMs, it's the same because both turbos are now at full boost....but with NS you have that full boost earlier in the game and that definitely helps.

 

https://www.rx7club.com/forum/showth...ght=sequential

 

OK fist of all... It DOES make more power in a race aplication, you can talk all you want about Max hp being the same, but overall through the rpm range the non seq produces more hp. I stand by my first statement and the explaination of that statement 100%!

 

If you guys are drag racing your not going to see a difference from seq versus non seq. I ran a 12.3 @ 113 with the bone stock seq set up. The ONLY mods I had were intake, full exhaust, PFC running the base map and 12-13psi of boost. My 60 foot time was 1.89 and thats with the seq set up. I was running the stock IC, stock clutch, stock suspension, stock wheels, stock everything else. I was running a set of worn out Nitto drags.

The point of all that is just because someone does better with non seq doesnt mean that the non seq itself is better, its all about that drivers abilities. If you launch your car at 5K which is roughly the best place to launch no matter if your seq or non seq then you will be running both turbos the entire time. Its not going to make a bit of difference if you seq or non. Sure maybe if you launch at 3K when your not even in your power band but what the hell does that matter??? It just means that the driver isnt launching in the powerband like he's supposed to so its totally irrelevant as far as I'm concerned

The only exception to this is if you do the FULL seq conversion and remove a little restriction, it will make a SMALL difference on the top end and maybe throttle responce but from what I hear make the car MUCH louder!!!!

Seq versus non seq is just trading 2500-3500 power for 3500-4500power. Thats it, your only messing with the seq transition, not max power. The power your swaping isnt even considered when racing anyway cause you NEVER drop below 5000rpms

If anything on the street I would rather have seq cause you dont have to launch at high to make power which means more traction.

Its that simple,
STEPHEN

 

I am sorry but you are wrong about there being no difference in any form of racing. I'm happy for you for running faster than riki with your seq setup(not you seq turbo's thats responsible for that), but the non is faster and better for your car. If you really, in every race NEVER go below 5000 OK have it your way...

I give up...

 

I never said anything about "any form of racing" I said drag racing, read my first sentance.

Thank you for agreeing with me that seq/non seq setup isnt responsible for times cause that exactly what i was implying. The fact that the seq or non seq doest mean much to drag racing.

If you shift at 7000+ your not going to drop below 5000 rpms. 5000+ is the strongest point of the powerband and when racing thats where you should be. If people dont understand that then maybe thats the explanation for all the slow times I've been seeing out of heavy modded cars.

If your not driving in the strong point of the power band then your not racing. Gears are there and matched to keep you in the powerband.

Non seq might be faster if you drop your foot down at 3500rpms and leave it there but that doesnt mean anything. Thats like saying my car is faster than yours if you start in 2nd gear. When racing you drive within the poweband, any thing comparing otherwise is obsolete.

STEPHEN

 

I agree with drag racing and launching at 5K...then it make very little difference w/ NS vs S.

But I have to disagree with power swap, trading 2500-3500 for 3500-4500 power. The power is not the same. The power from both Turbos at 3500-4500 is a lot stronger than the power from just the primary Turbo at 2500-3500. I will sacrifice the weak power at 2500-3500 for stronger power at 3500-4500.


Mark