cant get more than 10psi boost why?
 

Ok as some of you know i have been working for some
time to get the boost up on my stock computer
run 20b.
I have a modified stock computer that will
boost to 16 psi in a cosmo but will not in my rx7.
the best boost i see is 9.5 psi max.
it hits 9.5 then drops to about 6 psi as the 2nd turbo
comes on then goes back up to about 8 to 9 psi
then as the revs pass 5500 to 6000 rpm the boost
drops off to 4 to 5 psi, i assume this is because the
stock turbo's cant keep up at the higher rpms.
anyone have any ideas as to why my 20b will not
get up to 16 psi and why a stock / modified 20b in
its cosmo body will?
Sounds to me like a 3rd gen like problem with a vac hose
off or a solenoid not working but i have replaced the vac
hoses with silicone and everything seemed to be working.
matt

mine was like that, and it turned out to be the 270degree bend ic pipe, that right there was worth 2psi. another thing to look at is the exhaust.

mike

the exhaust is 3" from front to back, no air box.
if it's the ic piping i should still see high boost pressure
at low rpm's . I am sure the ic piping has lots to do with
the low pressure at high rpm and that will get addressed
soon.

matt

you might also check the wastegate solenoid, its the one on the tb elbow, should be blue and red

mike

hey now, where did you get your modified ecu? im thinking of just running the stock ecu for a while. is it actually possible to squeeze 16psi out of the stock turbos? others were saying that some sort of turbo upgrade would be necissary (thats why im considering having BNR rebuild my turbos, but then i run into problems with the computer). a modified stock computer would be great! i would love to run the turbos in sequential mode if at all possible (is the modded stock computer set up for running sequential??) thanks!! -heath

yes this computer is a 20b computer modified with new
fuel and ignition curve as well as a boost controller function
that allows control of boost between 13 psi
and 16 psi. there are a couple other things that were
done to this computer but don't apply to a 20b in a
rx7:) and yes sequential turbo control like stock.
the stock computer with open exhaust and intake will
make almost 10 psi as it is,,, but i want 16 psi!!! :)

later
matt

now, may i ask where you got such a computer? this would seem to be the perfect solution for a 20b project (can anyone interject if they feel differently?). now, do you have modified turbos?? i have been told numerous times that the stock turbos (in there stock configuration) will not be able to support that psi as they run out of volume of air at a higher RPM.

also in response to your problem, i was thinking that since your computer is meant to go in the cosmo, maybe (and this is just a guess) people that were able to see 16psi were using the stock cosmo airbox and exhaust...therefore less flow throughout the system and thus they could build more pressure without having to worry about running out of volume. maybe look into BNR to do an upgrade of your turbos, or do what pettit does and swap the compressors (i think they use a ht18 for primary, and an ht 15 or 12 for secondary).

the computer mod comes from re-amemiya in japan.
I was thinking of a bnr upgrade he wants 1650 to do
them.
you talk about swapping compressors where would i get
these parts?
the car this modded computer is out of had 3" exhaust
and cone filter so we should be very close to the same.
I was thinking of putting a line on the turbo side of the
IC and see what the pressure is there maybe that is
where the problem is, maybe it is making lots of boost
and its not getting to the intake.

matt

warning: this might be bad. pull the wastegate line off, and run without it, that way you know if its the turbos/restriction or something else. be very careful it might overboost and kill it

mike

I was thinking of trying that but am unsure if the
modded computer is switching to the high map rom
and if i do get a burst of boost without the extra fuel
i was worried that it might blow up in a hurry...

when you say pull the waste gate line off where do
you suggest i pull it off of ? at the solenoid or the turbo.
guess it doesn't really matter, the one on the top would be easier i guess..
matt

now, are you sure this car that the ecu came out of was actually making 16psi? id be extreemly careful if you disable the wastegate...there has to be a safer way to test the turbos, but im convinced that they are running out of volume....well except for the fact that you cant make high boot at low RPM. hmmm, i wonder if its something with the computer thats preventing high boost?

as far as swapping compressors, i think thats what pettit does. i believe they use the hittachi ht-18 from the tII (this may not be accurate...i may be mixing things up) and the ht-12 or 15 (cant remember) from the FD (again i may be mixing things up, but i think they use the FD primary as a secondary???). please dont quote me on this cause i have a bad memory for these things. ill try to find the thread that talks about pettits solution. the BNR upgrade may be all you need but i havent talked to them yet and dont know how far you could push their upgraded turbos...or how much restriction there is due to stock exhaust manifold.

how much did you pay for the computer from RE amemia? did you send a core and they upgraded it? also, do you know if they are readily available? thanks again. -heath

I am quite sure the computer was making 16 psi boost in
the car it came out of, it came from lance warren of
3rotor.com i seen a couple videos of it working in his car.
I would love to test it in a stock cosmo but there are no
cosmos around my area:( the cost of the mod from re-amemiya is very high, i was going to send
my stock computer over and have it done but i thought
getting the computer already moded used was a better
deal,,, i might have been wrong about that, will have to
see if i get it figured out.
I would love to know more about the parts needed to m
mod the turbo myself i would love to try and see what
happens. so any more details you can find the better:)


matt

Just a quick question,,, is there a way to control the boost
on the sequentials? is there a boost controller that
could be used on the 20b? i assume there should be
if the computer is chipped for 16 psi i would assume that
controlling the boost with some type of controller on the
waste gate should be possible?

matt

well a boost controller for an fd would work wouldnt it since they are sequential? do you have any sort of ballpark range for the RE Amemia upgrade? ok check out this thread -> https://www.rx7club.com/showthread.p...highlight=ht18 there seems to be some disagreement on what the actual turbos are on the 20b. can someone who is knowledgable interject and let all of us know what turbos are used for the stock 20b primary, and secondary? thanks guys! heath

ht15 and ht10, they are "upgraded" with the fc's ht18 and one fd ht12. i dont think it would be too hard to do, but i dunno never tried

mike

i wonder why they dont use the ht-18 and the ht-15, or 2 ht-15's? more boost no? do you know (for the 18 & 12 that pettit uses) which one is the primary and which is secondary ? wouldnt you get faster spool up with a small primary and larger secondary cause you could prespool the larger one? im gonna talk to BNR and see what they say. it would be great to have them swap the compressors and THEN do their upgrade for better flow and balance the whole assembaly.

the bigger one is primary. on the 20b all 3 rotors go to the front turbo and then upon transition rotors 1 and 2 keep going to the front turbo and #3 goes to the rear turbo

mike

thanks for the info Mike!! wow, thats quite a complicated design.... it doesnt sound like the most efficiant. also, wouldnt it make sense to use a smaller turbo for your primary, and since its sequential, pre-spool up the bigger one as you approach transition? i see why they used the smaller one since its only run off of one rotor but the design just seems really bad. i would dump everything into one pipe, then open/close vents to use each turbo. mazda always takes a strange approach to things but they must have chosen it for a reason.

by the way mike, what is your turbo setup? if your using the stockers, what has your expierience been with them, and how many PSI can you run? thanks again, heath

well my opinion is that 3/2 is inherently flawed, theres no easy way to do it. mazda as always was looking for a flat torque curve, so they picked a primary that spools fast by itself.

i'm running the stockers too, until they die. right now i dont have any boost control so i'm only running about .5bar (7ish psi), my goal is to run .7(10psi), maybe .8-9 (12-13) in the midrange and let it fall toward redline. the previous setup would run .8 in the midrange but due to a bunch of little things (weak spark, restrictive ic pipes) would fall to .4 at redline no matter what i did, its better now. i never tried to go higher; i want to go easy on the motor

mike

mike where would be the bast place to get
fc's ht18 and fd ht12 turbo parts... i assume that to mod the 20b stock turbos all that is being done it to use the
compressor wheel from the above. or is there more?
will these fc and fd compressor wheels fit without
machining the turbo housing?

matt

to get the parts prolly get used set(s) of turbos. i think the fd turbo would go in pretty easily. the inlets are the same diameter, so it might just be minor machining of the housing? or use the fd housing? i'm not sure about the fc turbo, i dont know if they are just putting the bigger wheels in the stock housings or using the fc housing. if you're lucky then the ht15 and ht18 have the same cartridge, and shaft size

mike

something to look into,,, the fc turbo is that a 88 or the 89?
i cant remember now but i think they were different.

matt

they have 2, 86-88 and 89-91. they both use the same compressor, the 89+ has a slightly different exhaust wheel in a redesigned housing

mike

so would a guy just change the compressor wheel or
both the compressor and exhaust sides?

matt

im guessing the whole thing? isnt it one balanced unit. wouldnt changing just one side upset the balance? and how would you even do that? hopefully all the turbos are interchangeable...which would make for a much simpler swap. this is all pure speculation on my part as i havent even pulled the motor from my front clip yet:biggrin:. im assuming we would want the newer ht-18? how about keeping the 15 and moving it to secondary, and adding an ht-18 to the primary side?

the only thng that worries me about messing with the turbos is from what mike said a few posts up

"the bigger one is primary. on the 20b all 3 rotors go to the front turbo and then upon transition rotors 1 and 2 keep going to the front turbo and #3 goes to the rear turbo"

if this is so and we change compressors, wouldnt we mess up the back-pressure ratios between the rotors. i mean with only the primary running its not a problem, but since the secondary is only run off of one rotor, wont we end up with rotor 3 seeing more/less back pressure than the others? how would this affect anything if at all? if rotor 3 was seeing more back pressure than the others wouldnt put it under more stress and make rotor 3 much more likely to fail? anyway, if back pressure ratios are not an issue then might as well keep the 15, move it to secondary, and add an 18 to primary. also if bnr was to rebuild/upgrade them we'd get even more boost :wink: -heath ps i cant imagine a used ht18 would be all that much... im gonna check out prices just for fun in the fc section...ill report back.

ok im seeing $50 (for an 18 that needs a rebuild, to $500 for one thats just been rebuilt)

Ill take the one that needs the rebuild:)

matt

yah you only need the wheels and shaft

mike

its in the FC parts section...search for turbo :wink:

ok i sent an email to BNR...this is what they wrote back (by the way check the top...they state that the 20b turbos are an ht-12, and an ht-18? mike said they were a 10 & 15... frankly i have no idea now???? i thought pettit *upgraded* to the 12 and 18...maybe that information is false and they are actually using the stockers??? if anyone has the inside scoop on any of this (come on 20b gurus i know your out there :biggrin: please enlighten the rest of us cause im confused!!!!) id also like to find out exactly what pettit does to their turbos since there seems to be some disagreement now...so if anyone works for, has worked with pettit on a 20b pleeease chime in!! heres what BNR sent me: (i will ask them about flow rates for the stage 1 & 2 options so we have actual figures to compare to)

//
Hey Heath.
_
We_can upgrade these turbos for you._ Here is what_we offer.
_
Bryan
www.bnrsupercars.com
_
20B Cosmo Twin Turbocharger Upgrades
_
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 “cartridgeâ€? 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 Â1/4â€? 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
//

also can someone knoledgable explain whats going on in the stage 3 upgrade? its starting to get a little over my head :wink:

last question...how does 500cfm compare to the flow rates of the popular singles (for all you single 20b guys :) ) thanks again, and please read the thread above this one too! -heath

haha im gonna be single if i put any more time into this 20b....... beat ya to it

Some common compressor maps:
http://www.majesticturbo.com/compression.html
How to use them (simplified):
http://www.turbosaturns.net/articles...r%20maps_2.htm
How to use them (expanded):
http://www.gnttype.org/techarea/turbo/turboflow.html

BTW, you need to double a rotary engine's rated displacement when using formulas made for crummy 4-stroke piston engines that only fire half as often as rotaries. :)

Cam has never mentioned the 20B turbo upgrade to anybody down here in Florida. It doesn't mean that it doesn't exist, but I have only heard about it through the internet. I would call them to find out, but Cam is never there, and the other people who work there don't know jack about anything except the standard Pettit products.

Neither of the 20B turbos look like an HT-18 to me.
https://www.rx7club.com/photo/showph...cat=500&page=1

You know its about time someone got some info on stage 3 upgrades for the 20b. I was curious about this last year when I asked BNR if it was possible to upgrade them. I didn't get much info back then. Anyways ROTORMOTOR, since they have already responded to your e-mail, could you ask them if the stage 3's can be run non-seq? Also whats the max rwhp they produce, and the max boost they can handle? Thx

im already on it.... waiting for a reply :wink:

also, do any of pettits 20b coustomers belong to the forum...ive got some q's for them.

Not sure about the customers. You know I'm hoping for some good results out of these turbos because if the Pettit car can make 550hp at 1 bar with their upgraded twins, I would think that maybe the BNR stage 3's (with their dynamic seals) could make a little more at a higher boost. I was hoping for maybe 650 rwhp max. This way I wouldn't have to go single and spend extra money.

same thought here....and then i could run sequential haha (dont yell at me...i know simpler is better....and ive had tons of problems with leaking vacuum lines in my FD.... but i must say i really like it when its running properly)
tvon: by the way what is a dynamic seal?

well i had a chance to play around with the turbo's
today, i started by pinching off the hoses to the waste
gate took it for a run and found that nothing had
changed, so wondering if i had the correct hoses blocked
i did the next best thing i put vice grips on the waste gate
rod so that it couldn't move at all, took it for another
run and same thing, i guess i have some work to do on
making the ic lines more efficient!
next I am going to put a pressure gauge on the turbo
side of the ic and see what the pressure is before the ic
i am guessing that the pressure on the turbo side
is as high as the little stock turbo's can make it.

matt

I believe those are the special bearing seals BNR uses for the stage 3's on the Fd. They are suppose to allow for lower friction and the turbos to spool really quick(so quick that running seq isn't necessary). Also, less friction means less heat buildup. A major plus when dealing with the 20b:D "GoodfellasFd3s" has a set for his 13b. Ask him how much he likes them.

thanks t-von. ill let everyone know when i get a reply from BNR...either way, from what matt says he is finding, we can all see that the turbos WILL need some sort of modification (be that something by BNR, or if its possible, swapping to larger compressors our selfs).

hey matt, i was wondering about how you proposed to measure the pressure that the turbos are actually putting out. is it true that through a restricted pipe you will gradually see lower pressure as you move farther down the pipe? or would it be that the pressure is constant through a certain configuration of pipe due to restrictions? i havent thought it through, but if that is the case you would not be able to detect a difference in pressure using your method. heath

I am going to T into one of the hoses on the primary
turbo, the one that is taped into the compressor housing
then connect the boost gauge to that and see what i get,
probably a broken boost gauge:)

matt

i did that on mine, i got a 4psi difference. with the new setup i need to check it again, but it feels better, i'm hoping for 2ish

mike

woops

I have been told by a couple cosmo owners that
16 psi boost is possible on the stock setup, so i am
guessing that my ic and pipes are nfg

matt

16 psi on stockers?:eek: Wow did they tell you how much power they were putting down?

stock cosmo with 3 " exhaust and intake,
with the modded stock computer that i am
testing they say 450+hp.
sure find it hard to understand why i can even get close
to 12 psi with the stock turbo's never mind 16 psi!
doing some more testing tonight to see if i cant get
more boost.
matt

ok, i finally recieved an email from BNR. i asked him a good number of questions about the different stages that they offered, and what model turbos actually come stock on the 20b. most of my questions were not answered and the responses that he did give were vague to say the least. im not sure i feel any more convinced to use them than i did before. i asked a bunch of direct questions, sent him the link to this thread, and told him that there would be a good market for him seeing all the 20b conversions that are/will be going on. basically i wanted him to do a comprehensive write up on his products/conversions so all of us could make our decisions accordingly.....anyway this is all he wrote back->

//Hey Heath.

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.

I will have to set down and make some HP figues. If you have any qestions, feel free to call.

Bryan
www.bnrsupercars.com
205 790 2514//

Re: cant get more than 10psi boost why?
 

ok here i am after some more testing to answer my own
question.
the reason that i cant get more than 10 psi boost is
because it would appear, this is as much boost as
the stock unit will make (on my car).
I put a boost gauge on both sides of the intercooler
and this is what i found.

at 2200 rpm the boost jumps quickly to 10 psi on both
sides of the ic, at about 4000 rpm both the intake side
and the turbo side drop while the 2nd turbo comes to
life, once it is up to speed the turbo side jumps to the
10 psi mark, as the rpm's rise the intake side boost
drops, at 7500 rpm in 3rd gear ( yes i was going a little fast)
the boost on the turbo side is a solid 10 to 11 psi and the
intake side has dropped to 3 psi. All this testing was done
while the waste gate was clamped shut.

conclusion, the stock turbo's seem to top out at 10 to 11
psi and flow about what the engine does at higher rpm.
if my ic pipes and ic itself were better flowing i might gain
a little more on the top end. either way i feel that the
turbo needs to make much higher pressures to deliver
the needed flow through the little openings of the stock
turbo housings.

I am working on a source to supply upgrade parts, will
have to see what he comes up with.

matt

thank you matt!!!! i, as well as everyone else really appreciate all the testing that you are doing, so thanks again. if we all work together i believe we can find a cost effective solution to raise boost pressure on the stock turbos. im still working on getting info from BNR, pettit and a few other sources. ill share info as i find it...

the one question i need answered before i can go any further is about the turbo models that come stock. since i have gotten conflicting info from the forum, and BNR i wanted to check the turbos myself for the models. ok, heres my question: does anyone know if there are model #'s or serial numbers on the turbos that would tell me exactly what they are?? if so, where on the turbos would this identification be? thanks guys, and good luck to everyone! :biggrin:

ps mike, just curious... do you have any idea how much horsepower you are putting down with your current configuration @ 10 psi or whatever you are getting?

now: hmm maybe your ic setup stops flowing, mine kinda felt like that, now that i have removed the 270degree ic pipe is a lot better.

rotormotor: it did 220rwhp with the 270pipe at 10psi, now with the better coils, and ic piping it feels a lot better, i'm going to say like 240-250rwhp@7psi.
we do have a stock ecu 20b running around to dyno too, so we can see where we are supposed to be