TNTUBA

iTrader: (1)

My car trapped 96 MPH in the 1/8th just like I auto cross it. I didn't touch the shocks or change the AOA on the large dual element wing.

Converting that alone to 1/4 miles stats would have it trapping in the low 120's....on stiff as hell A6's. If I removed the wing, took some rebound out of the front and messed with tire pressures....there is no doubt I could trap in the mid to high 120's.

And I don't spin through first and second. Odd.

18psi

iTrader: (76)

When I bench race, my car never spins. Runs 9's like a boss.

When I actually hit the quarter mile, I wheel hop like a basketball.

Odd

TNTUBA

iTrader: (1)

There are hundreds of videos on YouTube showing how my car doesn't wheel hop and cuts 1.8 second 60's on UNPREPARED concrete. At the drag strip it's gone 1.6 short times.

LOL at you calling me a bench racer.

It's amazing what a little chasis work is worth

ScottyP3821

iTrader: (2)

I found this sweet site for supercharged miatas

http://miatacharged.net

Monk

iTrader: (3)

Thread starting to go the exact direction I anticipated.

guss_bruss

Wow this thread has had a lot of responses since I was last on here, awesome discussion though guys.

I want a linear powerband my decision to go cams w/74 is purely based on the face that the power band would stay completely linear rather than with a 94 building full boost at say, 4k rpm, then tapering off till redline (hence acting similar to a turbo, which is not what i want, for this car. It's not that I don't like turbo's, I do like them a lot, but I have driven Turbo mx5's before and they seem to just ruin it *for me*. Yet to drive a supercharged mx5 so I am yet to see if this opinion of preferring a supercharger holds true. Also who doesn't want a lumpy idle.. sounds awesome :P

It's not about power for me, I like the N/A powerband of this car I just want to increase it but I feel ITB's wouldn't increase it enough so the next best is going charged.

Please tell me if I am wrong about the 74w/cams vs 94 comparison!!

18psi

iTrader: (76)

you got the link wrong, here you go

http://miatacharged.net

You're welcome.

Chilicharger665

iTrader: (2)

A -94 is bigger than a -74. The power curve will look similar, but the 94 will be steeper. At all RPM. It is attached to the engine with a belt and is centrifugal. The -94 will make more power everywhere, period.

codingparadox

iTrader: (2)

Yeah I think some confusion is being had between centrifugal blowers and roots-type here.

guss_bruss

No sorry I should have explained myself better, the confusion isn't coming from the roots style blower.

With the 94 I would have to bleed boost via a BOV or wastegate as it would blow my stock bottom end up if I ran it at full boost. whereas the 74 maxes out at about 200hp (before it reaches it's maximum rpm limit, depending on pulley's i'd have to run). This means I would effectively be using 100% of the charger to get my power, causing a linear power band, rather than getting a 94, building full boost (which would be about 10psi on a stock bottom end) at ~4k RPM and then bleeding the excess boost off, this would cause a huge increase in power till 4kRPM then little increase till redline.

Please correct me if i'm wrong! this is my interpretation on how the 74 vs 94 would work. I am trying to avoid spikes in power and have it as linear as possible.

nitrodann

Its torque not hp that breaks stuff (ie the 'limit' is in torque not hp.)

Im flat out so I dont have time to exlpain more but im sure you can google it.

Chilicharger665

iTrader: (2)

I am not aware of any person breaking a stock BP bottom end with a -94. No one has ever posted about surpassing 220 wtq with a -94 on a stock bottom end either. Everyone that runs a Rotrex on here isn't even getting the psi out of the -74 that they should be in the first place. I reaaally doubt you will break things with the -94. I suggest you call Jackson Racing and get them to first tell you all about their kit and then lie about the release date.

ScottyP3821

iTrader: (2)

haha nice I like what you did there

wannafbody

iTrader: (1)

Not really, torque and HP are the same number............................................ .....at 5250 rpm.

patsmx5

iTrader: (16)

I can't tell if you're joking or serious, but Dann is 100% correct. Torque and HP are Not the same thing.

Torque is twisting force. It's what twist things and breaks them.

HP is power, which the equation for includes Torque and RPM. (force, distance, time)

Mobius

iTrader: (2)

Just run a bigger pulley on the 94, then, so that the torque ramp looks like the 74.

But I'm not understanding why you think building boost to a plateau, and holding it there, is inferior to slowly building boost all the way to redline to the same boost pressure.

Lincoln Logs

iTrader: (1)

I must be doing something wrong then...85mm pulley on a C30-74 and I'm seeing almost 9.5psi @7100RPM.

18psi

iTrader: (76)

isn't 9.5psi what everyone is seeing? and expecting 10-11?

Lincoln Logs

iTrader: (1)

A lot of the dyno sheets I've seen floating around report less PSI than I'm recording. Mobius comes to mind here, I believe he has the same sized pulley as me and is barely hitting 8psi.

My understanding has always been the stock 88mm pulley most of the kits ship with is ~8psi. 85mm is 9.5-10psi depending on redline and the 75mm pulley will hit 12psi peak while redlining the blower at 7200rpm.

Mobius

iTrader: (2)

Sean one thing to keep in mind here is you are running the -74 on a 1.6, so you will see higher PSI for a given compressor speed than a 1.8.

With the 80mm, on the stock engine I saw about 8psi, 191whp/156wtq.

With the built engine / CNC head, 6.5psi / 217whp / 166 wtq.

On the built engine, because the ATI superdamper is 145mm compared to the stock crank pulley's 135mm, I ran the 88mm pulley. 145/88 yields a slightly lower drive ratio than 135/80, meaning at any given rpm on the built engine the compressor was slightly slower than it was on the stock engine.

It seems none of us can replicate early power measurements with the C30-74.
Bellwilliams track car: "We made 230whp with the same set up at 7000rpm, 110krpm and a 1.6" restrictor (blower inlet ID is 2.375")." I don't recall which dyno they were using for that car.

LukeH's 99: " Running it with a 150mm crank pulley which spins it to 116k rpm(120k is max). It shows just over 12 psi at redline" Dyno was 234whp/178 tq.

LukeH's dyno was a dynojet, so expected to read higher than the Dyno Dynamics I use locally. But even taking out 10-15%, that's still closer to my number than I would expect given the cnc head.