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Old 04-11-2015, 04:15 PM   #21
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Originally Posted by turbofan View Post
Wat?

Oh. Added 76% more power.

And here's the dyno you've been looking for, and incidentally, it's exactly where you guessed it to be.

https://www.miataturbo.net/build-thr...4/#post1175668

Edit: OK it's not the JR rotrex kit, but it's a rotrex on a relatively stock NB. Almost completely stock NB BP6D.
ya, my bad. 76% gain or 176% of original power.

I can't imagine the JR kit being much different output wise. I guess it would come down to the efficiency of their intercooler kit and tune they provide. Well pulley size and what not too.
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Old 04-11-2015, 05:36 PM   #22
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e85 on most the cars I tune tends to add 50-100hp depending on the setup/flow/etc.

comparing 91 to e85 is just silly.
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Old 04-12-2015, 11:57 AM   #23
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Originally Posted by turbofan View Post
Wat?

Oh. Added 76% more power.

And here's the dyno you've been looking for, and incidentally, it's exactly where you guessed it to be.

https://www.miataturbo.net/build-thr...4/#post1175668

Edit: OK it's not the JR rotrex kit, but it's a rotrex on a relatively stock NB. Almost completely stock NB BP6D.
Relatively stock? He has CNC head and full exhaust. Also VVT+square top.

And even before he added CNC head and square top he had an NB2 engine which is supposed to be more like 125-130 at the wheels.
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Old 04-13-2015, 04:18 AM   #24
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That dyno is on a stock NB2 engine, before CNC head and square top and other stuff. And it's still a BP. It's a BP6D instead of a BP05 but still a BP.
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Old 04-20-2015, 11:21 PM   #25
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Originally Posted by cool hand luke View Post

I asked what ultimate PSI the standard 30-74 was of, and the guy at jackson racing said 10 psi, this seems low vs some of the threads I've read. Is this truly the PSI limit?

Second, the guy said you gear via pulleys to develop whatever your target PSI is at redline. why can't you spin it faster, build up to your target boost level earlier then bleed off the excess pressure so you can get to max boost prior to redline?

also, almost all the kits i saw had a HP at 160-180 on 7 psi. I'm assuming this is where the stock injectors/stock computer run out of room. With big injectors and a megasquirt is the 74 capable of 240 hp?

also, I've seen some kits that offer optional 30-94 upgrades, the rotrex site lists a 30-84 that's splitting the difference and from what i can tell would be right at what i was hoping to get, is there a reason these aren't used?
With a 98mm compressor pulley (which was stock diameter for the original KW kit), no restrictor, the C30-74 will make just under 10psi at 7200 rpm. Spun faster, as with a 75mm pulley, max boost will be around 12-14 psi. 10psi will get you about 205whp and 155-160 tq with 315cc injectors and a programmable fuel card piggyback on an otherwise stock 1.8. With bigger injectors and a standalone, you can get around 225-230 whp.

The C30-74 will move 536 cfm at its max rated speed; the C30-84 moves 554 cfm at the same max compressor speed, not a big increase worthy of moving up to that compressor. The C30-94's max compressor speed is lower than the C30-74/84 by 20,000 rpm, but it flows 675 cfm, a substantial increase over the C30-84 or -74. With a properly built bottom end, some head work to improve flow, and proper fueling and management, the C30-94 should be capable of well over 300whp in a 1.8 engine.
'Twas a time, someone had a 1.6 with the C30-94 making over 300 whp.
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Old 04-20-2015, 11:47 PM   #26
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Quote:
Originally Posted by Burnout View Post
With a 98mm compressor pulley (which was stock diameter for the original KW kit), no restrictor, the C30-74 will make just under 10psi at 7200 rpm. Spun faster, as with a 75mm pulley, max boost will be around 12-14 psi. 10psi will get you about 205whp and 155-160 tq with 315cc injectors and a programmable fuel card piggyback on an otherwise stock 1.8. With bigger injectors and a standalone, you can get around 225-230 whp.
nope- your numbers are high (for a c30-74)- I can guarantee "an otherwise stock 1.8" and a fuel card is not going to make 205whp. Probably more like 170.

fyi: stock KW pulley on my kit was 88mm; and a 75mm pulley will over-speed the compressor at 7200 engine rpm. I have an 80mm pulley and am not getting 10psi.
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Old 04-21-2015, 12:03 AM   #27
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Originally Posted by dcamp2 View Post
nope- your numbers are high (for a c30-74)- I can guarantee "an otherwise stock 1.8" and a fuel card is not going to make 205whp. Probably more like 170.

fyi: stock KW pulley on my kit was 88mm; and a 75mm pulley will over-speed the compressor at 7200 engine rpm. I have an 80mm pulley and am not getting 10psi.
The actual PSI that you get vs HP will depend on how well the engine flows the air in and out. You will read a lower PSI on a ported head with larger cams and free flowing exhaust but have much higher power output than a stock head with higher PSI.

Power is related to how much oxygen gets to be burned which is air density (ie psi) multiplied by volume per second (ie flow).

This means that quoting PSI in relation to power output is misleading unless you know the motors are alike.
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Old 04-21-2015, 10:53 AM   #28
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Originally Posted by Madjak View Post
The actual PSI that you get vs HP will depend on how well the engine flows the air in and out. You will read a lower PSI on a ported head with larger cams and free flowing exhaust but have much higher power output than a stock head with higher PSI.

Power is related to how much oxygen gets to be burned which is air density (ie psi) multiplied by volume per second (ie flow).

This means that quoting PSI in relation to power output is misleading unless you know the motors are alike.

Agree- I understand the difference between flow and psi. However Burnout is saying you'll get 205 at the wheels with a powercard, injectors and a stock 1.8. that's bullshit.
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Old 04-21-2015, 10:58 AM   #29
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Are there any actual dyno results for these things or is it all bs and chest thumping?
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Old 04-21-2015, 11:17 AM   #30
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Quote:
Originally Posted by cool hand luke View Post
Are there any actual dyno results for these things or is it all bs and chest thumping?
Both Mobius and Tomiboy have dyno'ed NB2's with Rotrex kits.

-Mobius has a CNC head, Squaretop (i think), full exhaust, standalone = 217hp
https://www.miataturbo.net/build-thr...8/#post1214066

-Tomiboy has stock head? not sure if exhaust, standalone etc = 207hp


I'm not hating on the Rotrex at all, it just seems like everyone says and thinks they make a little more power than they actually do. I like mine.
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Old 04-21-2015, 12:20 PM   #31
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Originally Posted by dcamp2 View Post
Both Mobius and Tomiboy have dyno'ed NB2's with Rotrex kits.

-Mobius has a CNC head, Squaretop (i think), full exhaust, standalone = 217hp
https://www.miataturbo.net/build-thr...8/#post1214066

-Tomiboy has stock head? not sure if exhaust, standalone etc = 207hp


I'm not hating on the Rotrex at all, it just seems like everyone says and thinks they make a little more power than they actually do. I like mine.
This what a lot of us are trying to figure, and its just going to take dynos from multiple people to do it. On one hand I see Emelio with a lot of experience calling the C30-94 a bit of overkill(tranny breaker) while elsewhere it seems like the way to go if you want more than very low 200s WHP. Seems like supers in general just don't overcome crappy head flow characteristics the way a turbo can.

Personally, If I am dropping 4K on a system that has no hot-side parts, I want it to be upper 200s capable and mid 200s without breaking a sweat. So C30-94 all the way. At which point the question becomes 'how lazy is the 94 vs the 74 at lower revs? My guess is that its not much, but that's just a guess.
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Old 04-21-2015, 01:05 PM   #32
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Originally Posted by Sparetire View Post
This what a lot of us are trying to figure, and its just going to take dynos from multiple people to do it. On one hand I see Emelio with a lot of experience calling the C30-94 a bit of overkill(tranny breaker) while elsewhere it seems like the way to go if you want more than very low 200s WHP. Seems like supers in general just don't overcome crappy head flow characteristics the way a turbo can.

Personally, If I am dropping 4K on a system that has no hot-side parts, I want it to be upper 200s capable and mid 200s without breaking a sweat. So C30-94 all the way. At which point the question becomes 'how lazy is the 94 vs the 74 at lower revs? My guess is that its not much, but that's just a guess.
Agree- and I see that you are in Colorado also- which means you'll probably never have tranny breaking issues. I'm thinking of selling my 74 to get a 94 when the updated kits come out.

If you're tracking the car (which is what Rotrex is good for)- who cares how lazy it is at low rpm's.
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Old 04-21-2015, 02:23 PM   #33
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Isn't there a large difference between running the rotrex restricted and unrestricted as well?

Meaning a ton more CFM unrestricted?
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Old 04-21-2015, 03:53 PM   #34
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I'll have some more information to contribute to this conversation at the end of this week. Just finished my V-Mount set up with a C30-74 and 85mm pulley. I've seen around 8psi at 6400rpm in my datalogs from street tuning. Given what I've seen on a few dyno plots, I don't see it having any problem making 9-10psi peak @ 7200RPM.



Once I get the 91 tune finished, I'll swap ID1000cc injectors and put E85 back in.
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Old 04-21-2015, 04:25 PM   #35
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Originally Posted by dcamp2 View Post
Agree- and I see that you are in Colorado also- which means you'll probably never have tranny breaking issues. I'm thinking of selling my 74 to get a 94 when the updated kits come out.

If you're tracking the car (which is what Rotrex is good for)- who cares how lazy it is at low rpm's.

Yeah, and I do have a 6 speed sitting in the garage that may or may not be healthy too

But I know from past experience that if I get to 250ish WHP and its happy and reliable, I am going to start turning it up either via pulleys/restrictor or engine work. If the -94 is good for 400HP as some say, I can see reaching 300WHP at altitude.

The hilarious thing is that I really just want a fun street car that has some top-end scream and not much need for adjusting this that and the other thing. I don't care all that much about power below 4, but if its starting to suffer above that its one more reason to just go turbo for me.
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Old 05-05-2015, 01:20 PM   #36
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Originally Posted by Lincoln Logs View Post
I'll have some more information to contribute to this conversation at the end of this week. Just finished my V-Mount set up with a C30-74 and 85mm pulley. I've seen around 8psi at 6400rpm in my datalogs from street tuning. Given what I've seen on a few dyno plots, I don't see it having any problem making 9-10psi peak @ 7200RPM.



Once I get the 91 tune finished, I'll swap ID1000cc injectors and put E85 back in.
We need all of the informations. Has it seen the dyno since all the goodness was completed?
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Old 05-05-2015, 03:35 PM   #37
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I'm in the process of tuning my Stock VVT + intercooler + 445cc injectors + 30-74 +MS3 (Thanks Rev!) initial boost shows 7 PSI with an 85mm pully at 7K RPM (with stubby racing inlet as opposed to my "quiet option" as shown in pic) once Ive done the best I can in Tuner Studio I'm off to the dyno and will report.
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Old 05-05-2015, 10:53 PM   #38
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Originally Posted by Sparetire View Post
We need all of the informations. Has it seen the dyno since all the goodness was completed?
Got busy getting ready to co-drive ThePass' car at Chuckwalla last weekend. I also found out I need to replace some leaking injector gromets and the intake manifold to head gasket, I managed to find some nasty leaks there. I should be on the dyno Friday night, I have an autocross Saturday for some testing. Here is a screen shot from datalogging last week, max KPA should be a bit higher once the leaks are resolved.

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Old 05-06-2015, 12:35 AM   #39
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I've got the kraftwerks kit on my NB w/ 75mm pulley, making ~12psi. Originally i was making ~8 with the stock pulley. The rotrex unit has a max RPM that it's supposed to be at and I think the smaller pulleys spin it past that, that said, the 75mm pulley has shifted the power band to a place where it's way more fun to drive, and that I don't feel the need to wind it out to the redline all the time. I've also got the TDR front mount kit (i got the SC secodn ahnd and it was from a time when the kraftwerks kit was not intercooled).

It's a bit late & I haven't read all the responses before mine, but if you've got any questions about it I'm happy to answer them.

FWIW, buddy has a M42 JR kit on his NA, his makes a cooler noise but even before my pulley I was able to pull on him easily, so there's that.
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Old 05-08-2015, 01:50 PM   #40
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C30-74

85 nose pulley with stock crank pulley about 8 PSI (this is the pulley Kraftwerks supplies with the kit currently, some early kits were 88mm)

80mm nose pulley with stock crank pulley about 10 PSI

75mm nose pulley with stock crank pulley about 12 PSI This spins the Rotrex to it's redline 120,000 RPM when you hit engine RPM of 7200
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