rotrex 1.6 vs 1.8
 

I got really scared, and disheartened. THEN I saw that this was probably on a 1.6L and then I felt MUCH better!

I'm shooting for 260whp on a c30-94 and stock exhaust, but I have a 1.8L VVT witha flattop.

Good luck with sale!

To be honest, even with larger motor and a 1.8VVT it will not feel as torquey as this setup. Back to back comparisons with a local 1.8VVT says that you may hit similar peak HP numbers, but the feeling is not the same. You really need a good set of cams to wake up the Rotrex's midrange power, none of which any current vendors offer as an out-of-the-box solution

I beg to disagree

https://cimg7.ibsrv.net/gimg/www.mia...196ba22a62.jpg

*edit: just realized this is a FS thread and not a discussion thread. My bad. Moving these 3 posts

rotrex 1.6 vs 1.8
 

originally from this thread:

https://www.miataturbo.net/miata-par...0/#post1345306

Wait, did I start a new thread? I'm so dumb. Sorry lol.

Huh, good to know.

DO you have any dyno plots before and after the custom cams? Did you just replace the cams, no valvetrain mods? Care to PM the specs of the cams you got made? (long shot, but no shame)

Wait, don't I have different camshafts than you did before your customs? Did your local 1.8vvt have a flat top?

You didn't. I split these posts away from his FS ad that you posted in so it's not cluttered up.

I disagree with his statement though. 1.8 vvt will still make more torque and power than a 1.6, and over a broader range, even with a rotrex, and custom cams are not needed.

That is usually the case, but I'm curious to see what difference just the cams made for him.

I don't think I'll be lacking in torque (totally will compared to a turbo setup) but if I only make 200whp or like under 200wtq, through the stock exhaust, I'll get cams for sure.

As a point of reference, my car made 196whp with a c30-74 with a 75mm pulley. This is on a stock VVT motor with the stock exhaust system on 91 pump gas. During that tuning session the car was seeing knock. I now have a racing beat header and a 2.5" exhaust that's ready to go on and going to a retune soon. My torque curve looks similar in shape to the 949racing dyno plot above but with my peak torque at about 5.5k and much lower numbers (160wtq).

What engine management were you on? What injectors? Do you think you were seeing knock because of the stock exhaust system?

I was reading that the backpressure on the stock exhaust is not a big of an issue with superchargers, while a turbocharger system would really not like it.

He was seeing knock because of 91. It is the worst. It will knock before mbt no matter what.

Oh ok. I'll just have to fill up on E85 when I'm in cali, and be careful filling up on my way over.

I will have to dig up the old plots, there was about a year of gap in between having stock cams and receiving my Kelfords. Prior to that I also had a set of Chikara Stage II cams. Hopefully the screengrab is somewhere on my hard drive. The local VVT does have a flattop manifold, if it matters - I'm on a stock 1.6 IM.

Feel free to disagree but I would like to see some data: numbers, empirical, etc. to support your statement. While your statement may hold true for two equivalent stock 1.8v1.6 setups, I feel that once you crack open the block or head these statements are no longer valid. Custom camshafts are indeed needed and you will know what I mean once you go to a larger exhaust camshaft, as opposed to the traditional larger intake/smaller exhaust options that everyone currently offers. This is because blown motors behave differently than N/A or Turbo setups, in order to take advantage of the mass of air coming from the blower, the exhaust needs to vent as much as possible.

Like everyone said, if you want to run aggressive timing - Go E85.

Read reply to 18psi, I feel that my perspective on the rest of the exhaust system is to have it as unrestricted as possible. Though this would not affect his knock threshold as much as the octane he is choosing to run.

No e85 around MRLS. You will need to run 100 octane or something.

I'm running a MS3Pro with 610cc Flow Force Injectors. As others have said, I think the biggest contributing factor for the knock is the 91 gas, I'm not willing to go through the trouble of having to hunt down an E85 station all the time, I could do a flexfuel sensor but that might be a future project. The exhaust system may raise the knock threshold a little, but I shouldn't be able to hit MBT. I'm curious to see what difference it'll make, I guess I'll find out soon.

Ok, that's good to know. I'll have realtime flex fuel by the time I'm on my way to MRLS. Maybe I'll tune a bit with 18psi on the 100 octane before hand.

Best I can get in utah is 92 octane. There are like three E85 stations in the state, all of which are in salt lake city. Nevada 91 is much better than cali 91 (IIRC), so I should be ok filling up through nevada.

You can always throw a bottle or 2 of octane booster in the trunk in case you run into problems finding the right fuel on the way.

5 Best Octane Boosters and Additives 2016 - MyCarNeedsThis

Nevada has the same shit gas that CA does. So does Arizona.

Thanks for the suggestion, but I haven't had good luck with octane boosters. They don't mix properly in the gas tank, and always cause bucking for me.

Oh well, I'll just have to not floor it the whole way. I'll be able to keep 120km/h the whole way no problem at half throttle.