Hey guys. So I got a used 1995 engine for my Miata. I was going to tear it down and put new seals, water pump, timing belt..etc on it. Well, that turned into pulling the head, which turned into bearing and rings. So I've got an engine apart on the bench right now.

My goal is ~225 whp from this build. It will take a while to get there. I want to work up to it. I chose that number because I have read many times that stock internals are good to about 250 whp, and should last an long long time assuming good tune. I'm using an MP62 supercharger and not a turbo, so I had to add parasitic losses in too. I've got an MS2 on the way.

Rods:
I'm not into buying 400+ rods for my engine, but I could buy some of the lower end options. Entry level Forged. Ebay Specials, whatever.

Headwork:
This is where my questions come in. I have a good BP05 right now. I'm thinking of lapping the valves (or maybe a 3-angle), doing a mild port and polish, polish the combustion chambers and pistons to reduce detonation and throw it on. I could either do that to a BP05 or change to a BP4W. I know the BP4W is better. How much better? What I dont want to do is "waste" money on headwork just to find I shot past my power goal at X boost, and used up my engines safety margin, or put it at risk. If I can get the power from boost, id rather do that, I think.

I chose this engine because of the 8.8:1. Maybe I should have gone with the 9. I'm not too worried about it.

Comments? How would you do it?

 

You're not hitting 225 on that thing with our crap gas. Or are you planning to use e85?

I'm really curious why you're opting to do all the junk to the engine yet limiting yourself with a blower when you can easily make 250 with a turbo, have more power more torque, and all around be superior.

 

I know I can get better numbers with the turbo. I'm sticking with the blower because I have a CARB legal setup. So I can make mild changes (pulleys, intake..) and just run it by the smog police. I can't do that with a Turbo, as there are no smog legal kits, less an old school BEGI

Plus, I already have the blower. I figure when I've tapped out the blower, I've still got the MS2 and Intercooler. I'll switch then. I't might take a couple years though. I'm even tapping the oil pan for the return, just in case

 

I would advice that you "get into it". I cannot imagine doing all of the labor required to put a motor together without swapping the rods for forged H-beams. Put in whatever cheap H-beam you feel comfortable with, but don't put the factory rods back in. I openly ridicule people who tell me they've rebuilt these motors for forced induction use without using forged rods.

I'd rather have a smaller turbo with more boost, but a blower I would rather have lower pulley ratios and less boost. If you have the head off and you have the funds for a BP4W head, do that. Do not waste a penny or a second on a BP05 head. You can fully port a BP05 head and you'll be lucky to match the flow numbers of a factory BP4W head.

Hotside or coldside MP62?

 

Yeah. I found rods on ebay for 200 bucks. I havn't read anything bad about them so I just might put them in after checking them out. I may find I regretted not putting them in later. However, if I cant "max" the limits of the stock rods on pump gas, do I care? Any bearing change with the forged rods?

I'm already a bit beyond max budget. So I dont see myself going with forged pistions or anything. I do wonder if it was wise to go with the 8.8:1s vs the 9:1s or the 9:5s. But I'm not worrying about it.

Hotside MP62.

 

I broke a stock rod at 220whp after ~30k miles and a dozen track days at 200-220whp. At 250whp people routinely pull bent rods out of motors that show no signs of detonation. IMO, any FI build should get forged rods, even if you're only building for 200whp.

Consider what you are spending on machine work, bearings, seals, gaskets, your time, etc. I hate the "while you're in there" argument as much as the next guy, but rods are the weakest part of the motor and they are just not expensive enough to forego. You can skip the pistons, billet OPGs, and ARP hardware, but don't skip the rods.

 

Savington: you have to remeber that these MP62 setups don't make so much torque:

see here: http://www.fastforwardsuperchargers....2&d=1303928340

229whp and 176ftlbs


OP: for 225whp you will need E85. I know I had water injected Coldside setup for three years. 14PSI boost and E85 gave me 234whp. With normal 99RON fuel it was knocking all the time.

 

The most torque I ever made with my 2554R was ~190ft.lbs.

 

Done. Got them. I bought the CXRacing ones and they look good. They were all close in wieght. I did grind just a touch off of one to make them all within .1g. I did the same to the pistons, and polished the tops. Hopefully building today.

The bolts dont say ARP on them like the other "cheap" ebay rod kits. But I'll use them anyway.

 

Unnamed rod bolts would scare the ---- out of me. ARP 8780s are super cheap, and even ARP2000 bolts are under $90 for a set.

 

Given that you can buy forged rods these days for $300 I don't understand why you wouldn't do it on every build. Only exeption would be an N/A build where you want the rods to be slightly lighter. Any boost build, low or high = forged rods.

I'd sooner re use stock cast pistons in a FI build than buy forged slugs and keep the stock rods if money was an issue.