DMRH

OK, a certain eliment of confusion has crept into this warped mind of mine.

I have to remove a single turbo conversion from a 20B Cosmo & re-install the factory twin turbo set up. The owner has had enough of the lag & wants some throttle response back.

With a car like a Cosmo (auto) you drive under 3500rpm over 90% of the time & waiting for the turbo to come on boost means your original intention of finding that gap or teaching some V8 ****** a lesson dissapears.

This guy has been fully convinced that making the twins NON-sequential will give better mid range power.

Factory setting for the change to the 2nd turbo is around 3200rpm. If its spooling & open to the intake under that then I think it will reduce the boost of the 1st turbo & produce lag. 1st turbo provides boost from 1800rpm.

I am sure I am correct on this however is anyone aware of an arguement in favour of the NON-sequential operation.??

I'm thinking of you Evil-Aviator already, your opinions are usually technically justified.

Turbo 3

iTrader: (3)

My first thought was what is the turbine A/R of the single and why doesn't this person use a smaller one to spool up quicker? Wouldn't that be the cheap/quick solution?

j9fd3s

iTrader: (3)

if you do a true non sequential (taking the doors out) you will get a slight power gain, probably in the midrange. also you dont have the dip and then spike as the twins do the sequential swtiching over, so its smoother.

i have my twins wired open, the doors are still there, so mine is like the factory setup after its switched over, and its laggy, i dont get much boost under 3200-3500rpms. its actually easy to do, theres only 2 things (the big 'tca' actuator on the bottom of the turbo, and the valve on the y pipe) to wire open and you need to tee the crv into the bov and its non sequential and you can see how you like it

mike

Evil Aviator

Lag = Boost, Boost = Power. Is it possible that he would be happier with less power? What is his current turbo and boost setting?

Isn't a V8 one of those engines that feels fast because of a lot of torque, yet gets stomped by Wankels that make their best power in the upper rpm ranges? Hint, hint.

Most people just look at the turbo. I look at the whole system as a loop. The engine feeds the turbos, and the turbos feed the engine. Each accelerates and decelerates at its own rate, causing a surplus or shortage of gas to one another's dynamic requirements. I think the question here is whether or not the engine can spool up fast enough to feed the two hungry turbos. I have no experience with this, and it is not possible for me to speculate on the different acceleration times of the two system types other than Mazda most likely took this into consideration with the initial design, and probably optimized the stock sequential system for "pizzazz" over power.

LOL, so does he want power or response? Let me guess... both?

Custom builders in the US have gotten good power from a non-sequential setup... for about $35,000 USD in parts and labor.

This attached graph may help as a comparison for power. The lines are smoothed out due to the coarse 500rpm resolution, but I think it is still good for general comparison. Keep in mind that the non-sequential engine may have the stock block and turbos, but it has a lot of external modifications and was tuned by a leading performance shop. Also, the dynos are different.

References:

Stock 70,000km C-series 20B.
https://www.rx7club.com/attachment.p...postid=1819419

Stock-port 20B with non-sequential turbos, standalone EMS, FMIC.
http://www.cris.com/~Asam/Dyno1.html

j9fd3s

iTrader: (3)

i'll take yellow for $200 alex....

see my point though, the stockers non sequential dont really do anything until 3500rpms....

mike

Evil Aviator

Just a guess, but I think that PFS charges a little more than $200 for the yellow.

Yes, I see your point, but this is also due to your other point about the sequential changeover power fluxuation. If you look at the original stock dyno chart, you can see where the sequence point causes that dip you see on the blue line of the Excel map around the 3500rpm point.

I have a feeling that a lot of the big power gains in the non-sequential dyno sheet are due to the EMS and FMIC more so than the turbo sequencing, but unfortunately I cannot support my claim with any hard facts. It's OK to make unsupported claims on the internet, right?

j9fd3s

iTrader: (3)

yah my friends 20b2000 (87 b2600 pickup with 20b and stock ecu) runs about 9-10psi, and its stock except for the exhaust and some of the ic plumbing to fit it in there.

how do you convert from dynojet to dyno dynamics? is there an approximation?

DMRH

Thats an awesome difference between the standard Cosmo.

Steve Butchers 1992 (stock) 20B version.

PFS 20B dyno.

Now, I wonder if the PFS 20B was using the standard gear like Steve Butchers Cosmo was. If the answer to that is "Yes" then I will happily set up the twin turbo's in NON-sequential operation.

Will even do it to my own Cosmo too. Such a huge difference.......

spanner

iTrader: (2)

Hey guys, as we're on this topic, is there any place that upgrades the stock 20B twin turbos ? Would it be possible to get close to 500hp from them ?
Either from the US or Oz ...

t-von

iTrader: (8)

You know thats something I was curious about a little while ago. The stock turbos themselves should be capable of that hp fiqure but, the real problem is the restrictive design of the manifold they are bolted on to. Truthfully, I don't think anyone on this forum knows of the twins true potential because of the manifold. Try Pettit racing & BNRsupercars. They might help!

Evil Aviator

Pettit makes 550hp with stock rebuilt turbos.

RotorMotor

iTrader: (5)

BNR will do their "stage 3" for like $2k which should be plenty of boost. and evil, i talked to pettit last week and got some info on their turbos.... they dont really do anything to them.... i think they do some ceramic coating and smoth out a 90degree bend as much as they can in the manifold. thats about it.

Evil Aviator

What do you get for that price? Tossing $2K at the small, stock turbos with their incredibly heavy cast housing doesn't sound like such a good value to me unless you are restricted to the stock turbos due to some type of racing rules.

Yeah, nobody seems to understand that. I think it's because nobody can grasp the concept that Pettit makes those power levels due to skill and competence rather than some shiny bolt-on magic parts and pieces from a Nopi kit that any teenager can install himself in 30 minutes with a screwdriver and a 12mm wrench.

RotorMotor

iTrader: (5)

damnit evil, i love bolt ons ... ok as far as BNR is concerned you get this with the stage 3 (from an email they sent me):

The 20B Cosmo turbochargers have 2 different types of turbochargers, one turbocharger being an HT18, and the other being an HT12. Although these turbos perform well from the factory, there is room for some power improvement. BNR offers 3 stages of upgrades for your 20B powerplant!





Stage 1: The stage 1 consists of a secondary compressor wheel upgrade. The compressor cover is machined to fit the upgraded compressor wheel. The primary remains factory. Both assemblies are inspected very carefully and they are each balanced/blueprinted to spec. The wastegate is ported to 30-35mm. All bearings, collars, and piston rings are replaced. All housings are very carefully inspected before used. All tolerances are checked before assembly assuring you quality in the work performed by BNR. RECOMMENDED FOR SEQUENTIAL OPERATION ONLY!



Price: $1250 with a rebuildable core







Stage 2: The stage 2 consists of both compressor wheel upgrades. Both compressor covers are machined to fit the upgraded compressor wheels. Both rotating assemblies are inspected very carefully and they are each balanced/blueprinted to spec. The wastegate is ported to 30-35mm. All bearings, collars, and piston rings are replaced. All housings are very carefully inspected before used. All tolerances are checked before assembly assuring you quality in the work performed by BNR. RECOMMENDED FOR SEQUENTIAL OPERATION ONLY!



Stage 2 price: $1600 with rebuildable core

Stage 3: The new stage 3 consists of the replacement of the factory CHRA (Center Housing Rotating Assemblies) or otherwise known as a “cartridge� for the secondary turbocharger. The secondary cartridge is modified and adapted to fit the factory turbine and compressor housings which is a very difficult task! The shaft is ¼� in diameter while the stock shaft is 5mm in diameter. The upgraded compressor wheel flows a calculated 500 CFM. The primary turbocharger is upgraded with a t04B compressor wheel and is machined to fit the factory compressor cover, while the turbine side of the primary turbocharger is clipped to spec. Both rotating assemblies are inspected very carefully and they are each balanced/blueprinted to spec. All bearings, collars, carbon seal, and piston ring are replaced in the primary turbocharger while the secondary turbocharger comes with a new CHRA.

Stage 3 price: $2100 with rebuildable core

Stage 3 is geared for both sequential and non sequential. The problem with the HT10/12 is the shaft is 5mm thick. The shaft cant take the Load that the larger turbo puts on it. Since the stage 3 has a replacement cartridge, it will be able to handle the abuse.

The 20B shouldn't have to be ported until you reach 550 RWHP. Then it will restrict flow.

Evil Aviator

I also like them if they are good.

That's the smallest HT-18 that I have ever seen, lol.

I would really like to see a dyno sheet with a 20B making 550rwhp with the stock ports. What is their reference for this? I don't think this is possible without nitrous.

What does this mean? I have never heard of anybody in the US with a sequential 20B-REW except for that one JC Cosmo that was imported.

The price sounds reasonable. What kind of dyno numbers are they getting with that setup?

RotorMotor

iTrader: (5)

^ about the ht-18... i was under the impression that it was NOT an ht-18.... i emalied them for clarification but they never responded. i think they may be mixed up?? i cant give any presonal input as of now cause my motor is still untouched in the front clip.

for them claiming that the motor would not need to be ported untill 550HP i dont know where they got this from

as for the sequential issue, an upgraded factory ECU can be purchaced ... someone got one from corksport, and NOW in canada got one from REamemiya. i know that NOW's is running on it.... i also know he has been having some issues though. id like to run my 20b sequentially on an modded computer with BNR's but im seeing that may not nessisarily be the best option.

i will be running my 20b off the stock computer and in stock formation (sequentially) to start out. im told that all the worries about using the stock ecu are crap.... there are a few people in hte 20b section using it without a problem. as far as ive heard, just unplug the tranny controller and youre good to go...only time will tell though
-heath

P.S. there seems to be (or is) alot of mis information circulating or being posted within the 20b forum (even within different companies regarding the 20b)... i like that the 20b is so "mysterious"... but i think that all of us working on 20b projects owe it to the forum and to other readers to be as accurate as possible. we need to ban together to create a reliable and consice source of information for ourselves and other potential 20b inquierers. im trying to rally the troops here haha!! id like to start a general thread soon to document my journey to come, and give everyone accurate info on the FACTS about the 20b that have not yet been "settled" ... such as weight (ive been talking to some of the v8 guys and they seem to think there V8's may actually be lighter and a better choice), stock turbo sizes, the myths (if they are myths) about running the stock computer, etc. sorry for the rant, i just feel like the 20b section is kind of disorganized and contains some misleading information.

Evil Aviator

Look for yourself:
https://www.rx7club.com/photo/showph...cat=500&page=1

Make a website so that everybody can read it.

RotorMotor

iTrader: (5)

ok, that is not an 18 on the 20b turbos then.... they're freakin small!! i think BNR is confused. on the flip side, pettit makes 550 HP with those teenie weenies at like 12-13 psi, so they must be decent... and think of the spool-up compared to a single!!

yes a website would be a good idea! its like 200 on my list of 5236 things to do regarding the 20b though..... soon, soon! for now the forum will have to do. -heath

Evil Aviator

The 550hp number is at about 15psi boost. Yes, the spool-up would be good.

j9fd3s

iTrader: (3)

but that means i'm a stinky tuner! if they have a magic part then i have hope!

oh and for our edification my buddies 20b truck is seqential also.


so far im not really impressed with the ns stockers, they are laggy, i dont really see boost until 3200-3500 rpms, i think a single wouldn't be much different there

mike

Attila the Fun

iTrader: (1)

Right! FWIW, I'll support them. And, yes, a little more than $200.

RotorMotor

iTrader: (5)

i dont know how pettit does it... either there is something we dont know, or theyre really just that good at tuning properly? however, if there is all this extra power available through proper tuning why would mazda decide to go with a 20b for the cosmo? wouldnt they rather properly tune a 13b, or a 1 rotor for that matter??? 550/3= 183HP!!! im sure mazda would have loved to throw a well tuned 7B turbo in a miata or something... it would be light as ****, and haul major ***!! something doesnt add up because mazda would not let all this "free" HP go that easily...especially with the 7 as they were trying to cut weight and production costs!!!

if its possible to crank 180HP out of a single rotor w/ a small turbo, the piston engine would have a lot of explaining to do!!!! this would be the ticket to rotary immortality..... think about what a single rotor would weigh -heath

Attila the Fun

iTrader: (1)

As Evil Aviator pointed out, the FMIC and EMC made a big difference. Giving credit where credit is due, knowing how to set the Tec-II units let Peter Farrell wring a lot more power out of the motor, even though the motor and the turbos were stock.

Using a boost controller to run the turbos way past their stock boost helped a bit, too. I read, somewhere, that a reasonable rule-of-thumb is 20 hp for each additional 1 lb. of boost. Do the math.

Attila the Fun

iTrader: (1)

1) 13B-rew housings - bigger exhuast ports equals more hp at higher rpm.

2) The previously mentioned turbo upgrade.

3) Porting the motor. (The chief mechanic for Kudzu Racing mentioned that he had once "thrown together" a turbo-20B for an enduro race. He mentioned that he did a "mild port", which he defined as less than a street port. The motor produced a reliable 550 hp., he said.)

180 hp per rotor isn't that far-fetched. Farrell was getting 600 hp from his 13B-rew drag car (700 with nitrous).

IIRC, there was a single rotor-powered motorcycle. It wasn't all that impressive from what I've read. FWIW, when Rick Potter and I visited Cam, at Pettit, in 2001, he was working on a 1-rotor motor. I don't know the outcome of the project, though.

RotorMotor

iTrader: (5)

ok but if everything is tuning (and port configuration) why wouldnt mazda go for efficiancy... how is there so much power to be had simply by tuning the ECU.... surely mazda knew this..... well maybe not (maz-duh)

PS about using the 13b-rew housings... if i sent my 20b to pineapple or something for a rebuild/port would they port my 20b housings to 13b-rew spec. or is it better to replace the housings? (this is in the distant future as my 20b is still in the front clip, nad i have to fix everything in my donor car's engine compartment from an engine fire before i can move forward)