EFR built motor build, 320 HP pump gas limit?
 

Hey folks.

I picked up an $800 '04 Mazdaspeed, and was doing some calculations today. Want to know what everyone might think (or dynoed) what the pump gas HP limit might be on this setup... approximately.

I calculated out that around 320 HP to the wheels the built motor should start to see knock issues on 93 pump gas...and by around 340 HP, pump gas shouldn't be used at all; E85 seems very much needed. Let me know if you guys see any glaring issues on this build.

For the block:
Full set of gaskets from Mazda Comp
8.5:1 Supertech pistons, ~0.0029" P2W clearance.
Wiseco rings, gapped to spec.
Manley rods
ARP main bolts and headstuds
Line bored main at a machine shop
Have the machine shop clean up crank
King XP Trimetal Race / ACL Race
Coolant reroute
'99 aftermarket headgasket(NVM, OEM MLS is better)
Boundary Engineering oil pump, shimmed
Gates racing timing belt
ATI Dampener
Oil pressure gauge with warning lights

Cooling:
Oil temp gauge
Coolant temp gauge
Crossflow Radiator
Oil Cooler w/ thermostat
Cut up junkyard hood with vents
Transmission cooler (?)

Head, Non-VVT MSM:
Deck the head flat, minimal material removed
8000 or lower revlimiter
OEM valve stem seals
OEM valve guides
Supertech heavy doubles valvesprings
Mazdaspeed OEM cams
Skunk2 Intake manifold + spacer, 2.3L Plenum Volume
OEM throttle body, red-locktite the damn screws

Turbo/air+fuel:
EFR 6758, softer wastegate with EBC
Flowforce 960cc injectors
Walbro 190HP Fuel pump (need larger pump, FPR)
AEM Wideband
Megasquirt 3, probably the Greek Basic model
Trackspeed kit probably...or DIY with a Kracken
Have a muffler shop fab a 2.75"-3.0" past downpipe
Giant magnaflow muffler everyone likes
WMI setup triggered by Megasquirt

The water/meth won't be tuned for, just used with a small nozzle as extra insurance post intercooler for the motor during track days. I have had good experiences setting up vehicles this way.

Idea is to break the motor in with low boost and just run low 200 wheel HP for a year or until we both get used to the thing on the track. Eventually would like to have a low 300 HP track machine. I think it is better to pick the 6758 and up the rev limiter to 8000+ RPM. Want to keep the torque low and just allow the motor to rev out for mechanical empathy on the transmission. With the 6758 we are at peak efficiency on the compressor map and that should be great for track use. Downside over a 6258 is slightly slower spool and response but I dont think really matters with an extra 1000+ RPM up top.

We have roughly a $10,000 budget just for the powertrain, going to start a build thread after we pull the motor and send it off to get machined.

What do you guys think? Low 300 HP stable on pump gas or did I fuck up my math doing the compression with the head?
https://cimg0.ibsrv.net/gimg/www.mia...39df5eac21.jpg
Our $800 '04 MSM

I think your biggest issue is going to be that hood.

99 aftermarket head gasket?

Huge mistake, unless you are going with a high end one of some sort.

Walbro 190HP will not be adequate. Yes and that hood.

please explain
I'm struggling to even comprehend this

Crank that thing up until you get real knock not made up paper numbers

Gotta butcher it for airflow and probably clearance. :( Probably going to grab a junkyard hood. No AC, no power-steering though so it makes piping a bit easier.

Was going to be something like a Cometic MLS probably. Yeah, you are 100% right on the head gasket, I didn't realize the Mazda OEM ones are MLS too. Good catch, thank you man. I'll go with an OEM one to match to coolant reroute.

Just doing a Walbro 190HP to get everything running right with the OEM fuel pressure regulator. Going to swap to something bigger before we decide to up the boost much. Eventually I probably am going to put in an aftermarket fuel pressure regulator and a 225-ish flow Walbro or Deatschwerks...you also should probably rewire them too since the OEM wiring doesn't look good enough, so that it why I'm sticking with a 190HP until I need more fuel. I think the Deatschwerks pumps are better than the Walbro, but I haven't looked to much into them. Plus I want a spare fuel pump that works with OEM stuff in case of troubleshooting problems. Can always fall back to a 190 HP + OEM regulator.


Lof of educated guesses and scotch. Checked out the head cc, bore, stroke, thickness of a standard headgasket, the supertech 8.5:1 pistons, etc, etc. Found a few people's posted volumetric efficiency tables in Megasquirt running EFR turbos and similar setups, what kind of spark advance they are running, etc. Print out an EFR 6758 and EFR 6258 compressor map. Make guesses about efficiency of a bunch of things. Open up a few engineering books / motor building / performance books, grab scotch and some relaxing music.

After that, I got napkin math of about 25-28 psi (40-43 psi absolute) on an EFR 6758 compressor map would flow "around" enough lbs/min of air for about 400 wheel HP. Checked out some dynos to make sure I'm not full of shit. Found an EFR 6758 Soviet put down 400 HP at 26 psi. However the problem is, peak cylinder pressure is too much for pump gas, derp. So, redid a few things and make a guess that around low 20 psi(+/- a few psi) on a 6758 would be about as far as I could take 93 octane and that would be in the low 300 HP range to the wheels. Check a few posts, seems reasonable based on what dynos you guys put down.

My error bars are fucking huge, but it is close enough to what you guys are seeing. You guys are a godsend read concrete dyno data.

Did the napkin math and compared it to real world dynos people posted. Seems reasonable, but I'd rather know what I need to expect before I turn up the boost.

Ok so just a guess. No big deal. Before you waste any money, I would learn some more and I would also revise a very healthy chunk of that parts list.
spending money on "temporary" parts is just wasting money and wasting time. do it once, do it right, enjoy.

Thank you for the reply, I've been reading here for months and I think I'm getting close to having a (non-shitty) working knowledge of the platform.

Well besides the fueling deficiency I'm going to have initially, anything you think would be better/worse?

For the pistons, I think the Supertechs fit well for my needs. This is going to be "streetable" engine, at least initially...think 225-250 wheel HP for a while with tons of room to grow. I like the Wiseco pistons, the alloy is much tougher. However, the alloy expands too much to get a tight piston to wall clearance that I want for a motor you can put some highway miles on. If this was a pure race motor I'd probably just do the Wiseco pistons loose like they need and just rebuild the motor semi-frequently.

I need someone to shit on all my decisions so I can make a better car. I do absolutely have to rebuild this motor though. Headgasket is gone, picked the car up with good compression on cyl #1 & #4 but the compression on #2 & #3 indicates a bad head-gasket. Checked it out with a borescope and there is indications there was water in clyinder #2 & #3 as well.

Mudflap, do you have a build thread? You did something very similar to me, but I didn't see a thread after searching for a few minutes.
Thanks!

Figured out how to search by threads started, nothing to see here.

yeah and my build thread is about as up to date as my fashion sense.

I have been looking with interest at the EFRs since they look like the logical upgrade from my GTX2860 FM setup, however most only really seem to sing on E85.

Is this more of a generic limitation of the BP or would perhaps the next size up EFR be needed for say 350-400whp on pump?

I wouldn't plan to rev to 8000+ for just doing track days and not competing for a trophy. Our agricultural style engines don't like it and longevity really suffers. Frequent rebuilds will be in your future. You will definitely want an aftermarket harmonic balancer to add to your list for the horsepower and RPMs you are contemplating. Fluidampr or ATI.

Unfortunately, our engines are not built like smooth Honda engines which seem to rev with impunity. The horse power levels you are contemplating, coupled with the RPMs you are suggesting, will have the crankshaft looking like a jump rope.

Your radiator may not be large enough for over 300 horsepower sustained. You will definitely need an oil cooler. You may possibly need additional cooling for the transmission.

Thanks for the reply.

Damn tractor motors, alright...8000 RPM or lower. Yeah, the stock dampener looks like it would do nothing past 6000 RPM. I'd probably snap the crank without something there.

What usually fails first? Accelerated bearing wear, crank snaps? I've got a 4000 lb crane and an engine stand, so I'm not scared to replace the bearings if I get a bad UOA from Blackstone Labs. However, stripping the block bare and sending it off to a machine shop semi-regularly is a PITA. Everything would be FUBAR with a crank failure.

I'll add the cooling to the list, I was already planning on a crossflow radiator, cut up junkyard hood, and oil cooler. Never thought I'd nearly spend $500 on a fancy crossflow radiator but they are the way to go for this platform. Pretty standard stuff. However, transmission cooler in a Miata is new to me...I'll look into it. Makes sense, 15% of my HP is converted to heat in the tranny under load. I just usually associate tranny coolers with automatics.

Det prevention is a limitation on all motors and turbos, the BP being more affected due to it's inferior flow characteristics.
Moar flow = good
Moar octane = gooder
moar both = goodest

As for OP: a BP4w is not a B18c, spinning it high is very unrewarding.

If you look at an EFR 6758 compressor map at the point pump gas becomes a problem, you are already at the peak efficiency of 74%. Going up a turbo size is only really effective in getting more power on 93 octane if you are way off the compressor map.

An example of this is my 1.6L Ford Fiesta making 300 Wheel HP on a Garret GT2556 with an upgraded compressor wheel. In cool weather, it will dyno about 300-305 HP to the wheels at 26.5 PSI of boost on 93 octane fuel. Does about 270WHP-280WHP in hot weather. It is WAAAY off the compressor map, but the car doesn't knock and I still have good spool and ~5% HPFP fueling left in 30F weather.

Lets *assume* I was currently knocking in my Fiesta. Going up a turbo size and keep boost at 26.5 PSI would make me run very lean, so I would have to drop the boost to around 22-23 PSI, and I would have less knock on 93. I would dyno around 315-320 Wheel HP before I ran out of fueling on a larger turbo.

However on the Miata at 93 octane limits, going from an EFR 6758 to a EFR 7064 moves my compressor from peak efficiency at 74%...to peak efficiency at 76% on the next size EFR's compressor map. So, .76/.74 is 1.027, or a 2.7% increase in efficiency. Here, going up a turbo size is effective from a 6258 to a 6758 for pump gas use. However, if you are trying to stay on pump gas, a 2.7% efficiency bump in the mid 300 HP range isn't going to cut it...the 6758 is pretty efficient as it is.

Instead, let us look at a fanciest more efficient and newest turbo, the Garret GT25-550. It has a peak efficiency of 80%. Looking here versus the EFR6758, you are again roughly in the peak efficiency island on the compressor map...so .80/.74 is 1.08, or 8%. At 320 HP, 8% efficiency increase will put you around 345 Hp. Granted this is napkin math, but the number are somewhat realistic.

So, a we take a huge spool hit for just a...25 HP increase in power before we again hit pump gas limits? Isn't worth it. This is only a ancient, port injected, tiny 1.8L motor. You have a pretty hard limit on how far 93 octane can get you...that just happens to be somewhere in the 300 HP range. With the peak cylinder pressures you would see, I don't see it physically possible to have a safe 93 octane tune anywhere in the 350-400+ HP range on this particular 1.8L motor. If you had direct injection or better designed heads with the right profile cams to drop dynamic compression...maybe you could do it. If you had a 2.2L-2.4L motor, you could probably swing it.

I would really aim for a much lower RPM. I am running a 6258 and it pulls like a freight train from 3500 up. I think Emillio has said in the past, expected engine life by RPM on track. 7200 was 100 hrs 8,000 was like 15 hrs.IIRC


anyway, I dont know your track experience, but i am pretty used to going fast. It would be foolish for me to go out on track with 350 hp. in city, this thing is a hand full. Every single time I drive it, even if its to the store real quick, I get a full dose of adrenaline. every single time. because its insane. 1st through 3rd just spin, 4th is approaching 100 mph in about 8 seconds.



My current opinion on a turbo track miata is this:

is my annual budget for fun things in a miata 20-30k a year? if yes, then go for 3-400 hp. Thats what it will cost for 10 track days a year at that power level.. Someone correct me if im way off.

If you dont have that to spend, then set 225 as a realistic goal, and probably a yearly operational cost closer to 10 k for 10 track days a year.

All of the above figures are all cost inclusive.

Well, it isn't the worst designed motor I've seen at least.

Well, if I need to keep it under 8000 the EFR6258 might be worth looking at again. I'm going to have to call Trackspeed in the next couple of weeks anyway and have a talk with them anyway, they'd probably have a very good idea on which one would work better for my uses.

I've got autocross experience and right under a thousand hours in racing sims with an expensive wheel, stick, and three pedal setup for my PC. I'm somewhere between Novice and Intermediate as far as experience goes. I've got enough skill to know about 225-250 HP is about as much as I can handle right now in a Miata sized car. The Fiesta is about 270 WHP heatsoaked at 2600 lbs...but FWD is way easier to drive at the limits. Rear end gets loose? Just floor it, works every time.

So would you say that BPs on pump are limited to low 300s on an EFR because they're knock limited and adding more boost will just create a lot of heat as the timing will need to be very retarded? So then the only way to get a big increase in power would be to run something with a very free (and so very laggy) turbine?

Sad for the lack of E85 here :(

I don't see any mention of turbine flow, which is arguably the more important factor when you are looking at detonation resistance. Compressor maps only tell you half the story.

Your guesses are quite good, BTW - 320-340whp on 93 octane is just about the real-world limit. A little lower on CA91.

Remember that the 6258 and 6758 use the same turbine side, so the only reason to select the 6758 would be for high-boost efficiency. In the real world, those two turbos are going to make extremely similar power figures up to around 20-22psi. Only past that, where the efficiency of the 6258 falls off dramatically, does the 6758 begin to actually make a difference.

If you only want 350whp, the 6258 is the correct option. There are multiple examples of that turbo making a legit, uncorrected 415whp+ if all the other ducks in your pond are in a row. If you must have 400-450whp, then the 6758 is recommended. The 6258 might not stretch to 450whp no matter what, but the 6758 will get there with its pants on its head.

RPM really doesn't make a big difference, it's all about airflow. People will be along shortly to disagree, I'm sure. IMO, the turbo doesn't care whether you make 400whp at 6000rpm or 8000rpm, it's the same quantity of air moving through the system either way. Yes, the VE is slightly different. Call me when you have a verified accurate VE table for a BP engine and I (and several others) will pay you a princely sum for the data. Until then, you're guessing, and the difference between 6k and 8k is within the noise of that guess.

7000rpm is the correct answer when the question is "what RPM limit do I want for long-term track reliability". There are specific reasons for revving higher, all of which involve a combination of "I hate money" and "I want to win the races I enter".