C30-84 vvt motor dyno: 213/173
 

Hey guys did a dyno tune today with blacktrax.
(Thanks @Twibs415 for a solid street tune for Jei to build from)
2001 nb2 on ca91 octane w/ ac and no ps
DYI MS3 pnp
C30-84 rotrex with 2.5 inch cold side, 2 inch hot sidepiping with a fab9 stage 1 intercooler
75 mm pulley, saw 9.76psi of boost on the dyno
Squaretop manifold with port matched skunk2 tb
Id1050xs, dw200 fuel pump
Unopened Stock motor @135k miles
Rb header, 2.5 roadster sport with hiflow cat exhaust

213whp / 173 tq on a dynapack

Next steps: e85, possible headwork with a engine refresh and also try to drive the damn thing.

https://cimg6.ibsrv.net/gimg/www.mia...911e4c6657.png
https://cimg3.ibsrv.net/gimg/www.mia...33e3340e70.jpg

Seems a little low on boost. Already checked for boost leaks?

Prior to the tune, Twibs and I did a leak test, and found no leaks from Rotrex -> engine. Did find that I'm leaking oil out of the rear of the engine somewhere :vash:

Theories we have on the 10 ish boost is restriction on the exhaust side: i'm running a stock head & a 2.5 inch exhaust with cat. If I were to port the head and remove the exhaust, I should be seeing more boost.

Increasing flow will decrease boost as it's a measure of resistance to flow.

In surprised it made that little power especially on a dynapak. I would've expected at least 240whp with an MS3 and an -84.

I'm prepping my car for a -94 and would have disappointed with less than 250 on that setup either a 94. Makes me slightly worried as it seems that half of people either make meh numbers or are really good.

I make 9 psi at 7000 rpm with a 80 mm pulley and a C30-84 / NA8 engine. Compared to other builts it is on 1 psi less. But I'm 1900 ft above sea level.

Also I've got stock header, stock cat and a 2 1/4" catback.
Thought about a restriction because of the cat aswell. But as bopob said, it shouldn't cause a pressure drop.

Haven't dynoed it yet.

213 whp isn't to bad for 91 gas. I guess 240 is only possible with 93.

This particular dyno is known to read 8-9% low compared to other dynos in the area. That would put this up in the 230 whp range, which sounds about right for an -84 with a squaretop on 91.

Is the statement above correct? I have the same intercooler, and the inlet and outlet are both 2.5".

Thank you all for the feedback / comments. Definitely welcome the discussion!

Jei's dyno is a known heart breaker. It makes lower numbers than other dynos from what I've read.

Please share your dyno experiences. The more data the better. Knowing that this a turbo forum, our rotrex data is lacking. Buddy went from a 2.75->3 inch exhaust with his rotrex and his boost went up as well as power. I'm wondering if by opening up the exhaust you do increase flow, but the increased flow identifies other bottlenecks in the system and there boost increases?

True that. :party:

Yes. On the hotside I went with 2inch piping for easier routing around between the ac compressor and radiator fan. I use a 90 degree 2->2.5 inch coupler on the hotside of the intercooler.

That's not what your original post says.

I made 213/175 with the C30-74, 80mm pulley, and the old Kraftwerks intercooler. Since then, I've upgraded to the Fab9 Stage 1 intercooler, and went from 1.75" to 2" hotside tubing.

Good call out, updated the post.

What octane fuel and type of dyno?

Have you dynoed the car since?

Fwiw a stock na8 puts down about 97hp on this dyno on a good day.

Can someone explain this with the ideal gas equation?
We all know that there is pressure loss in the boost pipes and the intercooler due to inner friction. Why doesn't that count for a cat and a exhaust pipe aswell? Why should this cause pressure rise and not drop?

Doesn't make sense

93 Sunoco. Dynojet Model 424XLC2 at All Aspects Motorsports in Chesapeake, VA.

I have not. However, go here.

https://www.miataturbo.net/superchar...rcooler-99360/

Overlap of camshaft profiles is why boost went up. Clearing out more pressure (bigger exhaust) on the exhaust side netted less back pressure during overlap against the supercharger.

here’s a question for you guys, lots of you guys are seeing around 10 psi on stockish motors. While myself and k24 are also seeing about the same with cams and heavily worked over engines. Wouldn’t the general theory be that with more flow would mean lower psi?

Yes.

Jei's dyno is indeed a heartbreaker. I've seen full bolt-on K24A2s do 205/170 on that dyno.

To confirm or denie that, I take a pressure-log next weekend when I upgrade from the stock cat to a 2,5 inch 200 cpsi high flow cat. Let's see!