Low on power with mods

[Hoffbrohaus]

Just got it dynoed and it's lower than expected (140whp). Unfortunately they didn't monitor afr. So I'm trying to reverse engineer what has been done to the car to get it running well.

PO mods:
Mark D chip. 93 octane
M30 AFM
Big Bore Throttle body
19lb injectors
Adjustable fuel pressure regulator
Super Sprint Exhaust (catless)
Looks like new wires and rotor

I put in new plugs. Smoke tested, no vacuum leaks. Emailed Mark Dsylva but no answer yet. One thing I noticed during the dyno at redline I'd get a puff of white smoke. So I think I need to figure out if I'm rich or lean but could that alone bring my power way down? I've seen cars with similar mods putting down 160 or more to the wheels.


Dyno.pdf

[mpowerful]

The m30 afm and the markD chip may not be playing well. The signal from the afm will cause adjustment to the mixxture and it maybe drowning it. Especially if the chip wasnt tuned for the 19s either.

[digger]

go to a dyno and get AFR. until then dont guess.

i would not expect 160 with those mods.

[squidmaster]

A dyno with AFR would definitely be the way to go!

[jlevie]

You must have the AFR plot to find ot what is going on. The puff of white smoke is worrisome. I'd say not to drive the car until you have the dyno/AFR data.

My Spec E30, with no mods other than the spec exhaust, made 161/159 on a DynoJet on a 100F day. It would probably make a few more in cooler weather.

[Jaxx_]

AFRs from 11:1 - 13:1 won't make a huge difference in power over the entire curve, with that said, if you're richer than 11.0 you'd probably know it by smell and black smoke. If you don't have some soot build up on the exhaust that's another indication that you're probably not running rich.

I'm going to assume that you're running lean as hell. How do the plugs look? That's your first indication. Also check for freckles of metal on the plugs--if that's the case you're detonating and you could even destroy your motor if you continue to do moderate or hard pulls.

edit: Here's a photo I pulled from some domestic forum... This is aluminum on the plugs.

[rwh11385]

Um, that's exactly what I'd expect since I've dynoed my car with pretty much the same mods with pretty much the same results... 142.7rwhp, 143.1 rwtq to be precise.

jlevie's engine is a fortunate outlier. I wouldn't expect that from a 25 year old car with some bolt-ons necessarily. Alex S's dyno plots barely make more than that with a lot more $$$ thrown at engine mods than you.

[Cabriolet]

miles on the m20 and has it been rebuilt?
i would expect those #s to be 15+ higher each.

[digger]

160whp would be rebuilt and blueprinted and whatever else the rules allow not a high mileage tired engine

[jlevie]

Um, that's exactly what I'd expect since I've dynoed my car with pretty much the same mods with pretty much the same results... 142.7rwhp, 143.1 rwtq to be precise.

jlevie's engine is a fortunate outlier. I wouldn't expect that from a 25 year old car with some bolt-ons necessarily. Alex S's dyno plots barely make more than that with a lot more $$$ thrown at engine mods than you.

Well no, not an outlier. It is a built engine using all stock, unmodified, components. Those numbers are typical of a built engine. The engine that I built for my 87 325is restoration project made 153/151 with the stock exhaust. It probably would have made about 160 with the spec exhaust.

[rwh11385]

Well no, not an outlier. It is a built engine using all stock, unmodified, components. Those numbers are typical of a built engine. The engine that I built for my 87 325is restoration project made 153/151 with the stock exhaust. It probably would have made about 160 with the spec exhaust.

If people expect their tired 150K-250K mile engine to put down what you fresh, blueprinted one did, then they will be disappointed and look to blame the talented chip guy that their bolt-ons don't make more power than your "stock" engine.

Part of the power this engine makes is from the way it was built, and part comes from the exhaust. During the engine build the block was bored 50 over and all of the tolerances were brought to the ideal values, rotating parts were individually balanced and then everything from the harmonic balancer through the clutch (less the rods & pistons) was balanced as a unit. Rods, pistons, and position in the engine were juggled around to get the most uniform deck height possible. The real magic was in a meticulous head build. A matched set of springs, new guides, and new exhaust valves were used and we had the cam blue printed to bring it back to original shape. Naturally particular care was taken in fitting the valves to the seats.

The car has a Spec E30 exhaust, which is where the rest of the power come from. That is a two into one collector just before where the catalytic converters would be and a 2.25" (I think) pipe back to a single glass pack. The exhaust imposes no restrictions, though it is loud.

Hence, your built engine is an outlier compared to most people's dynoing their beat old ass engines with a few mods thrown on them. And they start threads asking why they don't have some people's stock M50 power with a chip and bigger injectors.

Compare to:

Here's my '88 325is M50B25TU+M3 Cams+ Chip 4th gear pull with a 5sp ZF M3 tranny and 2.93 LSD

http://www.youtube.com/watch?v=2DlIrIcBw-E

(Spoiler: 168 RWHP, 154 ft/lbs @ 5k rpm)

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165/168 2.7i and oversized vavlies and headers, etc.

http://www.r3vlimited.com/board/showthread.php?p=2591945

134whp/145wtq m20b27 with 885 top end and Motronic 1.3 upgrade, stock eta exhaust, stock airbox, stock chip, stock inj etc etc.

----

That's awesome. My 270k mile m20b25 (stock everything, from airbox to muffler) with a real Dinan Chip made 145hp & 143tq.

Exhaust on almost stock m20 = 143/152

http://www.r3vlimited.com/board/showthread.php?p=3331141#post3331141

The numbers look pretty decent, but below what a stock M20B25 in pretty good condition is capable of and well below what a race built M20B25 can do. I like to see around 152/150 for a good ordinary engine and about 160/158 (or a bit better) from a race built engine.

MAF, headers, exhaust m20b25 = 140/146

http://www.r3vlimited.com/board/showpost.php?p=3183487&postcount=1

I dynoed at 145whp with my 19# injectors and tuned accordingly Mark D chip...I talked to Mark D and he said he thinks those numbers are a little low...anyone have a dyno sheet with more power for this exact setup? Its an M20b25

What dyno? The results vary according to the dyno used with a DynoJet tending to read higher. 145rwhp is going to be about right for a 100k or more engine. The chip adds a little and injectors nothing. A really good head rebuild would pick 5-7hp (or maybe a bit more or less depending on the ring and bore wear)

Just dyno'd my bone stock 200k mile b25 today and it made 136 hp on dynojet.

On the Dynojet I got 136hp 140tq. Stock M20B25 except K&N box filter and 17lb injectors.

Checking in with dynojet results on stock M20b25: 142 peak hp, 145 peak torque.

Rebuilt cylinder head, serviced injectors, Mark D. 93 octane chip, long-tube Stahl headers, a K&N drop in -- 148.5 peak hp, 152 peak torque.

d.hitchcock

As I said, Hoffbrohaus's dyno numbers are what I'd expect and pretty typical for taking a tired and old engine and throwing bolt-ons at it. Not really comparable to the fresh 160 wheel horsies and torques of a built SpecE30 engine, because it's an outlier. It might be typical of Valley Motorwerks or other Spec engine builds, but a compete outlier to the average R3V M20B25.

[Hoffbrohaus]

Wow great feedback. It is a tired old motor. Not too bad 131k miles, but still no internal work. This all helps, Mark D. did mention my chip may be 10 years old and can't remember if he included 19lb injectors. Like I mentioned in my original post I'm just trying to figure out what all the POs did to the car. Before buying this car I had a friend mention it may be easier to buy a bone stock car than reverse engineer this one, I would say he's right.

My head gasket has a small leak and I'd like to check my valve lashing, so if I'm taking the head off it would be nice to plan out things like port/polish/blueprint etc. I have been checking out Spec E30 rules too so I may go that direction and pull all this stuff off. Starting out with NASA HPDE2 though so I have to work my way up.

btw Jaxx, no freckles of metal on the plugs but they are slightly white so I'm probably running a little lean. I will be headed back to the dyno shop soon to get afr, trying to work a discount since they didn't run it last time when they should have.

[LJ851]

I can almost guarantee your AFRs are way off on the top end, the roughness of the dyno trace and it's odd flat shape tell me that.

There is something holding back available power in your setup, diggers #'s are probably right on.


I was quoted above with my 136 whp , after that dyno run i found a MASSIVE exhaust restriction in my aftermarket downpipes which i have since repaired. It pulls noticeably harder on the top end now. That was with a stock chip too.

[rwh11385]

I had 130-140K on mine with a 40k-old rebuilt head plus 19lb and then 17.5lb injectors, M30 AFM, JC and then MarkD chip. MarkD trumped JC and Dinan on power and delivery/curve.

Honestly, the more HPDEs I did, the more stuff I took OFF my car. Chasing down and passing S54 M Coupe and E46 M3s with a stock engined 325is (no chip even) on 205 street tires was more fun than fighting for marginal whp with bigger but sometimes problematic M30 AFM, etc. Especially when they asked what was under the hood.

Sort out any issues and focus on reliability (replacing old hoses, engine mounts, etc.) instead of some arbitrary power number. E36 M3 17.5lb injectors + MarKD 93 octane is a pretty simple but fun package. Maybe if you find the problem you can get up to a healthier 150/150-ish, but it's pretty normal on these cars what you experienced.