Power limits by part
 

So. Intro thread done. Lurked for long enough.

I wanted to know what parts will need changing at when for my build, so i made this list. There is a lower and upper limit because, obviously, usage type affects life. Trackdays vs driving like your nan, etc

This is mainly so i can work out what power outputs are realistic, can set a budget, and start pulling the trigger on parts.

Would you veterans change anything? How off am i, country mile? Nail on head?

Thanks!



Part-----------------------Lower limit-------Upper limit

1.6 power, at wheels-------------------100
1.8 power, at wheels-------------------115
1.8 VVT power, at wheels--------------130

1.6 injectors-----------------140----------------150
6” (<1994) diff--------------100----------------175
1.6 clutch--------------------150----------------160
Cooling system--------------150----------------200
1.8 injectors-----------------170----------------180
1.8 clutch--------------------180----------------190
1.6/1.8 Conrods-------------225----------------250
5 speed gbox----------------225----------------275
Pistons (1.6?/1.8?)----------250----------------280
Fuel pump-------------------280----------------320
Oil pump---------------------300----------------350
6 speed gbox----------------325----------------400
7” (1994->) diff-------------350----------------400

EDIT: All in wheel HP!

There's your problem.

Pretty sure 1.8 Pistons can hold more than that

I guess it mostly depends on tire for drivetrain parts and tune for engine parts...

Axles let go around 400?
I know a few 1.6 rear ends on some 250hp cars too. Those things are weird. Some let go on stock power, some never die.
PPF's don't like a ton of power as well. Same with diff carriers.
Then there's the stock harmonic balancer.

Anyone have u-joint or drive shaft failures?

Thats pretty damning, ha.

Would you say that its accurate enough if done by the crank? Id assumed that everyone quoted wheel hp because of how dyno's work etc.

If i can get some better numbers ill update this, it could be a half decent resource. It took me ages to find it all...

Curly means that torque is the destructive force, not horsepower.

-Ryan

I really think pistons are stronger than they get credit for. It's just that very few people are dumb enough to install forged rods and leave the pistons stock. I put 25k street miles on my car at 332whp/303wtq before it was totaled and the stock pistons were still going strong.

I'd drop fuel pump down a bit, I think pretty much everyone over 250whp is running an aftermarket pump. I feel like mine is showing signs of struggling at 200whp. They're cheap and you don't want to find out that the stock one can't keep up when you're at peak power/boost.

The stock coils should probably join the list as well. Maybe 225whp-250whp.

Overall that's a good list.

Yeah if you've read around a bit on the forum, you'll realize it's "All in wheel FT/LBS!"

Some of the parts don't really need to be on the list either.

This can be calculated:

1.6 injectors-----------------140----------------150
1.8 injectors-----------------170----------------180

Who runs this little power...

1.6 clutch--------------------150----------------160

These are either glass or invincible. Replace it regardless.

6” (<1994) diff--------------100----------------175

This should be taken care of before/during turboing. Not based on power.

Cooling system--------------150----------------200

It is based a good bit on power. The more power you're making the more waste heat you're going to be putting into the coolant the more heat rejection capacity you need. Its also based on usage though. Some people can easily be running towards the upper limit of what the stock rods can take and be fine in their particular usage with the stock radiator and no re-route, IE they have no a/c, only see at most 3 seconds of boost at once, and live in the north.

^also dependent upon ambient temp/location in the world.

It matters if you are just doing a 10 second blast on the highway or a 25 minute session at the track.

TBF i guessed this one a bit. Sensible range? It seems so from what i have read, and i wanted to include it if just for completeness sake. Everything else is 1st dregree reserach from this forum.

I had another read of that link fooger, nice writeup. Nice to know how much HP i can afford...



Part-----------------------Lower limit-------Upper limit-----Unit (@wheel, unless rpm)

6” (<1994) diff---------------90----------------250---------lbs.ft
1.6 injectors-----------------140----------------150---------hp
1.6 clutch--------------------150----------------160---------lbs.ft
Cooling system (water)-----150----------------200---------hp
1.8 injectors-----------------170----------------180---------hp
1.8 clutch--------------------180----------------190---------lbs.ft
Ignition coils-----------------225----------------250---------hp
1.6/1.8 Conrods----------225/7500----------250/8000------lbs.ft/rpm
5 speed gbox----------------225----------------275---------lbs.ft
Cylinder head bolts----------Unknown, Above 250---------lbs.ft
Crank pulley/HB----------250/7500----------300/8000-----hp/rpm
Pistons (1.6?/1.8?)----------250----------------300---------lbs.ft
Fuel pump-------------------225----------------275----------hp
Oil pump------------------280/7500----------320/8000------hp/rpm
6 speed gbox----------------325----------------400----------lbs.ft
7” (1994>) diff--------------350----------------400----------lbs.ft

Half shafts---------------------Stronger than 7" diff
Propshaft-------------------Likely stronger than 7" diff
Crank/Block-----------------Unknown, above 500lbs.ft
Main bearing caps----------Unknown, above 500lbs.ft
Valve float(1.6?/1.8?)-------7500--------------8000---------rpm
Intake cam VVT--------------7400--------------7500---------rpm

PPF ?
Cooling system(oil) ?

1.8 axles break well before the diff, now what I dont know is if MSM axles break before the diff.

That is the first time i have seen mention of a VVT cam having an issue with high rpm... Has anyone experienced any sort of failure of the intake cam above 7500? Do we have any means to replace, reinforce, or otherwise rectify this issue?

Only reason I ask is because i will be using a VVT head on my next setup. i would like to address the issue ahead of time instead of having to fix it later

Its not above 7400rpm, its the area around 7400rpm. VVT head is totally cool with running 7500-7800 it just doesnt like the rpms near 7400ish because of harmonics. If you go searching back theres some old posts from many years ago on mnet about exactly what breaks. I know Sav told me when building my engine that the supretech valve springs took care of the issue entirely.

Ah, I got ya. Thanks for the quick update.
Andrew is building my engine as well, so this issue will be taken care of. I am still going to research failures for piece of mind.

My 93 is on 90k, I think its done about 20k of that boosted.

1.6 Viscous diff is quiet as a mouse.

5 spd box is kaput, dead, it is an ex-gearbox.

Just goes to show, er, something!

Question about cooling limitations. I am finishing a turbo build but havent addressed cooling yet. I am in the North East so outside temps shouldnt be above 60 for the next 5-6 months. Will I still have heating issues? Since it is the end of the season the car should only see 1 more autox before next year. Can I hold off until spring for street use? Car will have roughly 200 whp.

I broke my 1.6l diff in a parking garage no where near max TQ in 1st gear. So I think the 1.6L diff is just YMMV, be warned. lol.

These diffs seem a bit of a gamble! Theres gotta be some sort of random manufacturing oddity that makes the failures so sporadic. Or maybe they are super sensitive of not having their oil changed, i dunno. Ivw widened that range up, as well as a few other tweaks.

If anyone knows the limits of the half shafts, oil/coolant and the PPF, that will (should?) finish this off. Unless anyone knows different for anything else. Ive made my choices for power now.

Part-----------------------Lower limit-------Upper limit-----Unit (@wheel, unless rpm)

6” (<1994) diff---------------80----------------250---------lbs.ft
1.6 injectors-----------------140----------------150---------hp
1.6 clutch--------------------150----------------160---------lbs.ft
1.8 injectors-----------------170----------------180---------hp
1.8 clutch--------------------180----------------190---------lbs.ft
Ignition coils-----------------225----------------250---------hp
1.6/1.8 Conrods----------225/7500----------250/8000------lbs.ft/rpm
5 speed gbox----------------225----------------275---------lbs.ft
Cylinder head bolts----------Unknown, Above 250---------lbs.ft
Crank pulley/HB----------250/7500----------300/8000-----hp/rpm
Pistons (1.6?/1.8?)----------250----------------300---------lbs.ft
Fuel pump-------------------225----------------275----------hp
Oil pump------------------280/7500----------320/8000------hp/rpm
6 speed gbox----------------300----------------350----------lbs.ft
7” (1994>) diff--------------350----------------400----------lbs.ft
Propshaft-------------------Likely stronger than 7" diff
Crank/Block-----------------Unknown, above 500lbs.ft
Main bearing caps----------Unknown, above 500lbs.ft
Intake cam VVT--------------7400--------------7500---------rpm


Half shafts-------------------300?---------------???----------lbs.ft
PPF---------------------------???----------------???----------lbs.ft
Oil cooling reqd-------------???-----------------???----------hp
Reroute reqd----------------???-----------------???----------hp

Bryan has broke half shafts at 350? Launching the car at the strip. Maybe someone can go back through his build and confirm.

Bryan has also broke his PPF north of 400.

Bryan also broke his diff carrier (one of the ears i do believe) north of 400. (he does have 3.363 gearing which may be something to think of.

Perhaps someone should cruise back through his build thread and confirm some of this stuff. I can link him to this thread too, he may have some decent input. These are some of the lower end numbers of the parts as he drives his car pretty dang hard.


This is just my opinion, but a reroute should be required if you decide to do any type of forced induction and or track driving at all. Hell. I think it should be required even if you're in a hot climate.

Was making 205hp with 1.8 injectors when we had the 1.6 still in the car. Also can't believe stock fuel pump will support 275hp.

Thank you, i found that thread. Some good numbers. I couldn't see if MSM axles were being used, but i'd assume so. They are in the table now. Also took the easy way out on the oil/coolant.

I have also found a few good posts from savington RE revs, so theres a few entries in there for that now.

Ive added a thing for fuel pressure on the injectors, thats a good thing to think about.

Fuel pump: Fuel Pump - Miata Turbo FAQ

Anyone know how much pressure the stock injectors will take? I can work out the rest.
Also, PPF, and the upper limits of the half shafts (and now head gasket) are still AWOL. Also pistons.

I lied, more tweaks:

Miata2fast broke several halfshafts/cv shafts while naturally aspirated and running at the drag strip. 1.8 car using '99 head, cams, 12:1 pistons, carburetors, so 150hp?

Anyone know the limits of the stock fuel rail?

I'd say it's probably well above 200 psi. Maybe even well above 500 psi. Definitely greater than most fuel hoses, fuel pressure regulators, or fuel pumps.

Wait...This is the "power limits" thread. Certainly you didn't mean to insinuate that the fuel rail had a power limit, did you?

Yes, I did mean power limit. Surely the fuel rail has point where it can no longer provide a high enough volume of fuel for even distribution to each cylinder. If the flow limit was so high that we couldn't find it, there would be no reason for aftermarket fuel rails to exist.

Well marketing. I bought one because I couldnt find an FPR adapter for the stock fuel rail (because I was searching for miata parts and not shitty fwd mazda parts) and the fuel rail from 949 was cheap enough.

Most of them exist because people will gobble up any silly statement a company makes and companies make money that way. Most here have not found the limit of the stock rail, but if I had to guess I'd say it's somewhere between 450-550 or so

...I think it was hilarious that for years everyone was raving about dual feed rails, and many even made their own DIY dual feed rails. Then we go and prove that neither cyl 1 nor cyl 4 is starved for fuel, and now only a handful of people here run them, most of them "just because".


Also the nb2 is not making 130 at the wheels bone stock unless maybe its an msm

I think most people switch rails for easy use of an aftermarket FPR and easy clean AN connections. I know that's why i'm putting a dual feed rail on. More so than "just because".

That makes more sense, and is probably a good reason to run one.

So there's the real reason, OP :)

right... market a paper bag full of shit properly and someone will buy it. I get that.

I am simply trying to figure out if i will need more than a new fuel pump in my 2000 with 600cc/min injectors to be able to evenly fuel 300hp on 93 octane. The returnless miatas have a better stock FPR than the NA's FPR, so i am less concerned about the FPR being able to manage the larger pump. I cant find any info on where this FPR and fuel rail become an issue.

I am also having a little difficulty in finding a clean way to reduce the pressure differential between the manifold pressure and fuel pressure since the returnless FPR is at the tank. I am thinking i will have to route a manifold pressure signal line all the way back to the tank to get something like the FUELAB 545 to work easily for me.

Or you could just convert to a return style setup.

sorry for the slight threadjack... Thank you for the answers on the fuel rail. I speculated that its limits were rather high but didnt have any info to be able to back it up.

I think you're right around the limit of the stock pump/fpr actually.

Im keeping this to sub-400 levels, partly to stop the list growing to cover every part number of the car but mostly because if you are at that power level, you know what you are doing.

Both the bosch and delphi injectors seem to top out at 8 bar delta, which puts their max power potential at 230/280hp :bowrofl: (RC Fuel Injection)

Sixshooter, im convinced miata2fast's car would have been wheel hopping. 150hp seems ridiculous.

Still learning...

Idk about the trans numbers I’ve seen many people blow 6 speeds way before they blew a 5 speed

Lulz.

Solid trolling friend.

I think every thread (except build threads and stickies) should auto lock after 12 months....

/2¢

Don't ask them to add more features...We've seen how that turns out.

Absolutely not, that's retarded. The whole idea is that if you have new info to add or clarification to be made trying to find that spread across 5 threads would be redicculous. Imagine if the DIY Bilstein thread was scattered across 10 different threads

I seriously just read this post and was like, damn that guy knows what he's talking about, I'm gonna :likecat: him... before I realized that was me... 5 years ago.

Another 5 years of beating up OEM pistons on forged rods with no issues at all. 5 dyno's over 300whp (including a sig linked 330whp pull on a Mustang Dyno), a pile of 11 second 1/4 mile time passes, and probably 100k miles on stock pistons, no issues seen.

https://cimg2.ibsrv.net/gimg/www.mia...1f77019b18.jpg


I did kill a 6 speed @ ~370whp/320wtq, stock pistons, stock 3.90 torsen, stock axles never gave me an issue.