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Old 05-03-2016, 12:47 AM   #1
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Default Horsepower projection on budget build

So a week and a half ago we spun a bearing on our bone stock 1.8 at the track during a 16 hour race BOOOOO

So this is a two parter. One is it worth looking at the crank and provided the crank is ok, throw some new bearings in? So we think we spun a bearing because the piston rings were stuck open and we got crazy blow by until we had no more oil to pump. Engine started knocking and we pulled off the track. It only knocked for about 20 seconds. The reality is that we could open it up and find that the engine is toast.

Ok now for part two. we have a 1990 miata that we swapped the 1.8 into. Obviously there are alot of JY mods that can be done to "hop-up" a naturally aspirated 1.8 motor. So what kind of numbers can I expect from a 1.8 with the exhaust intake cam swap, timing advance to 14*, tuned AFM so we aren't running stupid rich, 2001+ piston swap for higher compression, 93 octane fuel, high flow cat back exhaust.

I know the timing advance gets you 10hp, the intake cam gets you another 10hp, tuned AFM get you 10-15hp, pistons get you another 10hp?

Is it possible to get to 140-150hp out of stock miata parts? Any other JY mods you guys recommend?
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Old 05-03-2016, 01:29 AM   #2
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If it's a 94-97 head, maybe 120whp, if it's a 99-00 head, maybe 130whp. If you don't shave the head. You have some serious reading to do, this is all well documented and can be found via searching.

Stock header, stock cat, restrictive AFM and intake, stock ECU, all not great for power. Also timing advance from 10 to 14 degrees is usually not worht 10HP. Neither is an exhintake cam.
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Old 05-03-2016, 02:43 AM   #3
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I doubt it'll even make 120, more like 110.

Start with a megasquirt and a junkyard NB engine.

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Old 05-03-2016, 11:27 AM   #4
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Timing advance is suppose to get you 3 to 4 horses, that's it. Engine power isn't simple math, if a header by itself gets you 7 HP and an intake system by itself gets you 4 HP it does mean that if you combine the two you will get an 11 HP bump. In reality it will probably be more like 9 horses.
I will be generous and guess a power output of 121 whp on your proposed build.
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Old 05-03-2016, 11:48 AM   #5
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You're in luck, I just dyno'd a similar engine.

It had VVT pistons, not 99-00, port/polish on the head, ex-intake swap, rabello cams, fresh rebuild, CAS timing advance, and sadly stock ECU through a MAF (94). It made 133hp.

I also recently tuned an old spec miata. It made an impressive 121hp with a ~$10k 1.6. Threw an old MSPNP1 on, deleted the AFM and it made 124. You're not going to make close to 130.

With those mods, through an AFM, I'd say 116.

Also your crank needs a re-grind.
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