Hey Guys,
A good friend of mine(Ivan) came by the shop today in his Mazda truck and we dynoed it. It has a bone stock 20b with dual borla mufflers to keep it on the down low. On our dyno dynamics dyno it made 240 whp and 270 lb foot of torque. That was at 7-8 psi and tapering down to 4 psi by redline. A highly modified stock turboed 3rd Gen makes around 280 whp and 220 lb foot of torque on this same dyno. Might need to get another 3rd gen and do this swap after all.

Brett.

 

Good info, thanks! Do you have the chart? I'd love to see it, and I'm sure I'm not the only one here...

I assume it was using the stock turbos in parrallel? Why was the boost tapering down?

 

Dont quote me on this but if he's using the stock ecu that would explain the psi decrease. You see since the Cosmo was only available in automatic form, the engine wasn't tuned to provide crap loads of hp in the higher rpm's. Anyways, I'm just assuming so someone please correct me if I'm wrong.

 

yes it was stock ecu and sequential turbos

 

Here is a dyno of a stock 20B-REW in a JC Cosmo. It shows about the same thing:
https://www.rx7club.com/attachment.p...postid=1819419
(Source: DMRH)

 

Why does the boost drop off like that? It seems like that defeats the point of having a sequential turbo setup which offers efficent and consistent boost throughout the entire powerband? Is that actually how its designed to be in stock form?

 

Good to see that the runs we did look almost identical to the one posted. I can see how the stock 20B with upgraded mods and another 8-9 psi at redline can make another 100 horsepower or more. 4 psi by redline is not taxing anything very hard.

Brett.

 

i need to take pics of our dissassembled turbos, the wheels are sooo cute. it makes a stock fc turbo (which is too small) look huge

 

Isn't Pettit making 500 some bhp with the stock turbos? Given, its a ported engine and they're running a good bit more boost, but I thought that the stock units were fairly capable.

 

already went over this...pettits turbos are not stock...USE YOUR SEARCH KEY

 

Sorry, I think I've read about half the threads on this forum, and its hard to keep track of it all sometimes, espically with things like what car was using what turbos, etc.

 

sorry, that was a bit harsh....pettits turbos have been massaged.

 

Thats okay, I'm usually the one barking at people to do a search on some other forums that I reqular / moderate, so I understand entirelly!

I did find some nice dyno charts of some 20B's running relativly high boost on the stock twins on catenet.net. It's the 20b with the T78 that I REALLY like, though...

 

um... please elaborate, because ive posted on most of those threads and have talked to pettit. as far as they have told me, they make no MAJOR mods to the turbos and can do 10-12psi till redline i believe. can you tell me what you have heard is done to the turbos???? thanks, heath

PS yes the 20b turbos are relativly small compared to a large single, but think about it this way.... the FD uses an 2 ht-12's sequentially, and the 20B uses an ht-15 and an ht-12 for a secondary.... they are bigger than the FD turbos, and a good amount of power (and boost!!) can be had with those! there are not too many complaints about the FD twins.... i do understand that the 20B is feeding another rotor, but thats why they use an ht-15 instead of the ht-12 as a primary

 

Cam is the first one who will tell you the turbos have been ceramic coated, balanced, blueprinted and well, you get the idea. I am not his pr guy but if you are interested in buying a set, I think he charges 2K for them.

 

i was told that the balanceing and blueprinting of the turbos doesn`t have much of a "performance" benefit just makes them more "sturdy".,they do this for the 13b turbos also, but again no real performance benefit there or at least that i`ve noticed, it does however reduce cracking and under hood temps

 

I don't think the stock 20b turbos are going to get you anywhere near 550 whp. 425 whp I can beleive with these tiny turbos running them at 15 psi or so however.

Brett.

 

i talked to alamo rotary today about their turbos.... they claim to be able to run 16 PSI untill redline. they remove a few things and smooth all of the casting stuff out (i also think they remove some solenoid stuff and the bridge in the exhaust manifold). these turbos (even though small) can hold their own. i cant understand the single turbo rage.... yes its simpler, but if you do a few mods to your stockers you can put out a good amount of boost. ceramic coating is a good idea as well.... i hadnt thought of coating the actual exhaust housing, but it sounds like a good idea. if you pull apart your stock turbos and do a few "upgrades" to them they really are not that bad. can the single guys give their oppinions? -heath

BTW how much boost do you single turbo 20b people run? i cant immagine the car being streetable past 16PSI

Also, to the folks using the stock turbos that say boost signifigantly drops as they rev higher-> are your motors ported, or stock?

 

The twins can only take you so far in making power, as discussed above... that is the reason for the single turbo rage (besides the simplicity as you stated).
When you want to make serious power (500 rwhp+) and/or run serious boost levels (16 psi+) the stock twins, although pretty good for stock, are insufficient.

 

I just had an opportunity to dyno my 20B fresh from Pineapple Racing and Corksport last Friday. We went really easy. Essentially we were just getting some runs in so that the already Modified Stock ECU can be re-burned to make some adjustments. At any rate, I am very happy to report that we were able to achieve 12 psi on the primary (secondary didn't yet come on-line -just about though) and at 3500 rpm, we hit 170+ rwhp and an impressive 235 ft-lbs of torque. This is a rebuilt 20B by Pineapple Racing - Installation by Corksport. It has 3rd Gen housings (new), a small street port, level 3 oil mods, and ceramic apex seals. The turbos were rebuilt, also. Single 3" exhaust. Once I get the motor broken in and the computer re-burned and dialed in, I'll post a chart.

 

another reason to go single i would think would be because of heat ,this is of course just a tought but i would believe since the single setup has less clutter it also tends to built up less heat ,under hood ...just a tought

 

yeah i was thinking the same thing....im guessing that theres more surface area w/ the twins. However, if everything exhaust related were to be ceramic coated i think you would do quite well. also, if the exhaust side of the turbos were ceramic coated, you should end up with greater efficiancy as the gap between the blades and the housing should be made even smaller. as well as ceramic coating (if done properly), porting all the cast stuff would be a good idea.... and also eliminating all the sequential stuff will make the already bottle knecked manifold more tolerable. in addition to all this... you can send the turbos to BNR (im not sure if they end up doing all the stuff thats listed above) but they can then do even more work to them (possibly larger housings, and new/moddified wheels & shaft etc).

now the things i am grappeling with are:

A) is this financially practical compared to going single (i bet the price would come out about the same),

B) what are the advantages/disadvantages? disadvantage-> more restrictive exhaust vs single = less power, advantage-> faster spool up times, disadvantage-> probably cant reach the same PSI as a turbo (but does your application really require you to need 30PSI?), disadvantage-> single is simpler... w/ less stuff to break, advantage-> the option of keeping it sequential, but realise your exhaust is even more restricted than non...... basically as i see it, if your main goal is to have a bad *** street car then it would be better to run the twins in sequential... if your main goal is ultimate power and not streetability than get a large single... i dont like the idea of running the twins non-sequential because i don't really see the point, if youre going non-seq then just get a single (**** or get off the pot if you know what i mean).

am i way off or does all this kind of make sense to everyone else out there? what to do w/ the turbos has really been driving me crazy recently. -heath

 

well the main problem with the twins is that you have 2 turbos heating up the oil and water.

plus the exhaust flow out of the twins is bad, and the stock dp is restrictive too (it necks down to a 1"x2" area).

 

As it is I'm planning to go with a single, but the turbo and it's accompanying parts will be among the last high ticket items I by, since they're by no means necessary to get the car up and running and in all honestly making plenty of power. I was debating with myself about it for some time, though.

My reasoning pretty much follows what Rotormotor listed:

1. Its much simpler. I had trouble with the stock twins on my 13BREW from day one, ranging from oil leaks to boost problems

2. Its not a whole lot more expensive compared to the rest of the swap since I can fabricate the manifold and piping myself

3. A properly sized compressor can easily provide the airflow that the 20B wants at even low boost (under 1 bar) to make gobs of power relative to the 13B. If I can make 400whp+ at under 14psi with fairly high efficiency (read: cool charge temps) then that's awesome. Sure, you can run the stock units at that boost level, but its not that great for either the turbos or the engine.

4. When run in parallel the stock twins function like one larger turbo. If you want simply performance with the perks of the twins in parallel, just get a small singe that will give you similar (or better!) spool with better max airflow.

5. Just check out these dynos!. That chart has a 20b with stock twins at 10psi, a 20b with stock twins at 15psi, and a 20b with a T72 at 14psi. The curve from the T72 is almost identical to the stock twins at 10psi from 2000 to 4000rpm! Now, the T72 curve is from rx720bt's FD with a ball bearing turbo and a nicely ported engine, so that makes a difference. The twins were probably run in parallel, and the engine was probably stock. Nonetheless, I think it goes to show that you can in effect have you cake and eat it to with the 20B if you put your time and money where it counts.

I want a 20B because I want to run about 1bar on a single turbo and have a nice broad power curve. I have no doubt that that's easily possible.

 

thanks for the dyno charts.... good info! i was the motor w/ the twins ported? if you look at the graph comparing hte single and twins (at 15psi) you can see the turbo lag in the begining of the run (not too bad by any means though... just comes online slightly later). also we can really see the twins running out of volume past 5K RPM... either they simply cant move enough air or somehting else is going on.... its very striking to me to see them basically stop in their tracks instead of slowly tapering off.... either the computer or something else (if its stock) is venting boot, or theyre just spinning so fast that they are not able to catch any more air (kind of like what happens w/ a water pump that is spun too fast... it just makes a hole in the water and spins) ... in any case something strange is happening.