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Old 01-14-2013, 06:51 PM   #1
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Default Rev Limit VS Intake manifold ?'s

Dear All Knowing Miataturbo.net,


Some backround:
I am ready to drop my motor back in for the 2013 season. It is a forged 1.9l 94 block that I had built with every intention to turbo to the 350/300 mark. It is comprised of 9:1 CP pistons/Eagle rods/ARP everywhere/ACL Race/BE Street/949 Superdamper. BUT I am using a completely stock 99 head that was simply cleaned, leveled and reassembled with new guides and stems. The funds and motivation for boost fell away when I started instructing with NASA 2 years ago. Now all I want is a n/a TT car.


Previously I had made 135whp with the stock 99 mani and NO vics and a stock 7200 limit.
Last year I ran a Blox b18 mani to 8000 on AEM EMS and made 142 at 7800. The honda mani LOST 12ftlbs at 4600 and was down everywhere except from 6800 out to 8000.

I am aiming to stay in TTE after a dyno reclass. The car is heavy as is, I should have no problem staying under the power/weight in TTE. I am trying to work with what I have laying around, which is lots of parts and not a lot of budget for more parts(supertech valvetrain)

So the questions to the committee here are these:
1. Am I a fool for revving a stock 99 head to 8000rpm?
2. Am I a fool for giving up 12ftlbs in an area of the curve I do occasionally use on track for gains of only 7hp made up top?
2b. Does my tuner suck or are these numbers plausible?
3. Before the motor goes back in, I should reassemble a 99 mani and wire up VICS, right?
4. Some other option, like the cheap volvo valve springs and rev this bitch out?


Pics for clicks?



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Old 01-14-2013, 06:55 PM   #2
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Here's my un-educated take on this:

1- with stock cams and stock head, I think so
2- yes. on boosted cars the results are very skewed, but some (like Sav) have shown gains everywhere. on an n/a your results sound about right. Corkys (and others) results also mirror yours...or really close
3- yes.
4- with stock cams and without headwork, why?
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Old 01-14-2013, 07:33 PM   #3
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Quote:
Originally Posted by doward View Post
So the questions to the committee here are these:
1. Am I a fool for revving a stock 99 head to 8000rpm?
2. Am I a fool for giving up 12ftlbs in an area of the curve I do occasionally use on track for gains of only 7hp made up top?
2b. Does my tuner suck or are these numbers plausible?
3. Before the motor goes back in, I should reassemble a 99 mani and wire up VICS, right?
4. Some other option, like the cheap volvo valve springs and rev this bitch out?
1. Yes
2. Yes
2b. No, those numbers sound correct
3. Yes
4. If you want
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Old 01-14-2013, 08:41 PM   #4
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How much does that POS weigh?
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Old 01-14-2013, 09:30 PM   #5
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I really like Sav's answer and Hustler's question
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Old 01-14-2013, 09:32 PM   #6
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How much does that POS weigh?
I rolled it across the tech scales last spring at 2520. Full interior, power window/mirrors, both tops. Street car really.

I suppose I need to pull my 99 mani out of storage :(

This Honda thing makes cool noise though.
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Old 01-14-2013, 10:53 PM   #7
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Are you using shim under bucket lifters? Free horsepower.
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Old 01-15-2013, 12:00 AM   #8
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How did u mount the honda manifold? It looks like you just filled in the stock holes and drilled out new ones to fit? Did you match the ports on the manifold to the head?

A lot of the ones I've read about which made a good difference have:
1) used a frankenstein combination of stock and honda to get an appropriate runner length for their desired power band.
2) had turbo so the added capacity of the plenum makes a bigger difference.
3) had a lot of development in their car and knew what they were doing.

How many of those points do you have?
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Old 01-15-2013, 12:11 AM   #9
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Why is revving to 8 so terrible?

If stock limit is 7200, a "safer" 500rpm raise is 7800, why is 8000 so dangerous? (own personal curiosity)
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Old 01-15-2013, 12:20 AM   #10
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Quote:
Originally Posted by Vilko View Post
How did u mount the honda manifold? It looks like you just filled in the stock holes and drilled out new ones to fit? Did you match the ports on the manifold to the head?

A lot of the ones I've read about which made a good difference have:
1) used a frankenstein combination of stock and honda to get an appropriate runner length for their desired power band.
2) had turbo so the added capacity of the plenum makes a bigger difference.
3) had a lot of development in their car and knew what they were doing.

How many of those points do you have?
Yes. Chopped off the Honda coolant inlet and most of the bottom side of the flange. Mounting holes between the two pieces are fairly close on the topside so some were filled, all new holes were drilled with a BP gasket laid down. Honda fuel injector holes were plugged with aluminum round stock, plug welded, then ported back to match the runners. Ports only needed touched up on the outsides of 1&4.

As far as your 3 points, the original plan was to turbo it. But after years of both car and driver development I decided whoosh psssh noises didn't really matter as much anymore. At that point I already had the Honda mani on the car. Just ran it as it was.
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Old 01-15-2013, 06:51 PM   #11
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Quote:
Originally Posted by theshdwconspracy View Post
Why is revving to 8 so terrible?

If stock limit is 7200, a "safer" 500rpm raise is 7800, why is 8000 so dangerous? (own personal curiosity)
Stock limit is 7000. At 8000rpm, you will stretch rods, break throttle body shafts, and eject the factory damper from the front of the motor.

These motors do not like to rev, and you have to dump a ton of money into them to get them to do it.
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Old 01-18-2013, 11:55 AM   #12
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Quote:
Originally Posted by Savington View Post
1. Yes
2. Yes
2b. No, those numbers sound correct
3. Yes
4. If you want
OR

1. Sell car

2. Buy racecar

3. Stop instructing

4. Race wheel to wheel

5. Give meaning to your life
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Old 01-18-2013, 11:57 AM   #13
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Quote:
Originally Posted by Efini~FC3S View Post
OR

1. Sell car

2. Buy racecar

3. Stop instructing

4. Race wheel to wheel

5. Give meaning to your life
Sell car, buy small tow rig (like 2000 lb tow capacity), buy SRF, race wheel to wheel. If I didn't love the miata so much and could actually drive in traffic at race speeds I'd consider it.
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Old 01-18-2013, 11:58 AM   #14
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lol

Those that want to rev these things out like crazy should sell, buy s2000, and live their life 9,000 rpm at a time.
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Old 01-18-2013, 01:24 PM   #15
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A ~300 gram Miata 1.8 piston on a stock length rod has ~1537 lbs of inertia force at 7000 rpm and 2,008 lbs at 8000 rpm. That's just the piston. At some point the stock rod will stretch a fraction of an inch, the piston will contact the head, and the piston will be set free from the bondage of the wrist pin.
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Old 01-18-2013, 01:47 PM   #16
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Quote:
Originally Posted by theshdwconspracy View Post
Why is revving to 8 so terrible?

If stock limit is 7200, a "safer" 500rpm raise is 7800, why is 8000 so dangerous? (own personal curiosity)
In addition to what others have said, it's not just that it's dangerous, it's that it's pointless. You're not making more power up there on these motors without completely changing everything.

Like 18psi said... wanna rev? Buy a Honda.
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