1986 325iX 3.1L Stroker + Turbo

[downforce22]

love this thread - always learn something from you. damn nice work on the tune. can't wait for some vid.. really want to hear that motor in action. I'll be pulling the trigger on a whodwho MS and 3.1 stroker next year hopefully. won't be going the turbo route though.

Cool to see 3.1L stroker kit whit turbo..Also see some results to how much boost it can handle and how long it will last. I have heard some saying that 3.1L stroker will not last so long etc etc..

thanks for the comments guys. I need to work on better videos for you guys. I love how my car is still running an M20... I got a comment from a local guy who i saw on the highway in his e46 M3 coupe, and he asked, "what's under the hood?' and when I told him turbo M20, he said it sounded great.

The car seems to be running great. i took it on mountain drives about 3 of the last 4 weekends and I don't even have to shift out of 5th at 11,500 feet (atmospheric pressure of about 9 psi or about 66 kpa). I have been wondering about the strength of the M20 as well. It turns out the S54 has a larger bore and stroke than my engine with the same cylinder spacing and still has an 8000 rpm redline.

My engine has 86mm bore, 89.6 mm stroke, 135 mm rod, forged crank, pistons, rods, 206.2 mm deck height, 9.5:1 CR

S54b30 has 87mm bore, 91 mm stroke, 139 mm rod length, forged crank, 216.9mm deck height, 11.5:1 CR

The main difference is the height of the engine which allows the s54 to have longer rods which keep piston speed under control with the longer crank. Because of this, I have my current rev limiter set at 6000 rpm. This puts the piston speed somewhere around 58.8 FPS This is an equivalent piston speed to a stock m20 (75 mm stroke) spinning up to 7170 RPM. Outside of piston speed I don't really worry much about the engine but have been cautious to run too much timing or too much boost without knowing what I'm doing.

http://www.csgnetwork.com/pistonspeedcalc.html

One thing I have done since the last post is I found a 3/8 NPT female bung and an 8" section of aluminum pipe that i could use to replace the AFM. With a GM IAT sensor I was able to remove the barn door and see how it changed the drivability of the car. One of the biggest differences was the instant response. It seems the barn door would be mostly shut on light throttle not allowing air through to the idle valve. Without it, there is less of an on/off bucking of the engine at light throttle positions. I had to use a blue silicone coupler to get it to work for now since the AFM inlet was 3", but I just ordered a black one to replace it. To connect the GM IAT, I had an old AFM that was junk that I took apart. I removed the male portion of the AFM connector and connected to the GM sensor to that so I could plug it directly in to the engine harness. I wrapped it in electrical tape to prevent corrosion and debris from damaging it, but I plan to rotatre the pipe upsidedown so the bung is on the bottom and the sensor and wiring is not visible.




It turns out the car is as fast as my brothers e39 540i/6.















And for the drive i took on Saturday I removed the heavy steamrollers form the picture above (17x7.5, 235/40/17, wt about 20+ lbs) and I put on this autocross setup (falken hanabi 15x7, 205/50/15, wt 12 lbs on RE-11a Bridgstones) but I ended up drving them in rain and snow at 9000+ ft. it is even faster and i managed over 25+ mpg.



And here is a video my brother took when I let him drive it about a month ago. 2nd gear, shifting at 4000 rpm, you can hear the wastegate dumping.

https://www.facebook.com/tom.schultz.547/videos/pcb.10154393314171389/10155496313680166/?type=3&theater

[digger]

the main difference between the 3.1L m20 and 24V engines such S52 /S54 is the piston barrel length/compression height/skirt length/materials and resulting piston to bore clearances. this is where lower durability can come into it as the piston and rings need to be kept as parallel/concentric to the bore axis to maximize life

[tschultz]

I like the Cripple Creek overlook photo, nice!

This photo was pretty neat also:




In the 540i I was foot to the floor through 2nd and 3rd gear. Into 4th you were approaching pretty quick in my rearview and I hadn't let off!

Of course we were at like 8000ft, but still the 540i doesn't feel slow at altitude either.

[bradnic]

great pic! I've been pretty adamant about keeping my IX coupe stock, but damn.

[downforce22]

great pic! I've been pretty adamant about keeping my IX coupe stock, but damn.

it can be a bit of a rabbit hole. For the cost of this car i could have bought another rwd e30 af turbod it a long time ago, but that doesnt have the same cool or rare factor.

I have been looking at my car decided I needed a few more datalogs. I went out and this is a run in 4th gear, slightly uphill at about 9 at night. atmospheric pressure was 80 kpa with intake temps at 65 F at the start. It is 17 seconds long starting at about 1400 rpm and going up to 5700 rpm. Boost starts building once I put the pedal to the floor. You can clearly see where the wastegate opens at about 2800 RPM and boost at 5.4 psig. I believe I am running a 0.4 bar spring (5.8 psig spring).

Boost creeps up and I had my boost cut set to 140 kpa (60 kpa above atmospheric, or 8.7 psig)

At 12 seconds my boost creep hits 140 kpa (8.7 psi), engine at 4750 RPM, boost cut turns it off so afr spikes and boost drops to 6.3 psig and as engine rpm rises the boost drops off. My engine AFR was climbing up in the 12s at this point so I may have to add some more fuel in the 4500 rpm range and 130 kpa area.

After a quick check of my 32# fuel injectors, they should be able to run the current power. At 6000 rpm and 9 psi with the temp/pressure conditions shown above, I am right at 85% injector duty calculated here (http://www.stealth316.com/2-calc-idc.htm). I have a couple 42# injectors and it may make sense for me to swap them soon.

Here is that datalog in 4th gear.


One thing to note, depending on EGO control settings, the oxygen sensor does nothing under WOT conditions. I have it set that there is no EGO control over 70% throttle so this is straight off my fuel map and I havent really tuned this upper section of the map. I will have to add some fuel and try again.

As you can see my boost creeps quite a bit from 6 psi to almost 9 psi. What can i do about this? It isn't a bad thing because it is sort of a boost by rpm, stay in it longer for more boost, but not ideal to have boost building with the wastegate open. I am running the TiAl 44mm MVR with a 1 foot bend and screamer pipe. Is it the manifold limiting my boost, or the turbo just flowing too much for this little of a boost pressure?

[aventari]

I'm building an M20 stroker with 86mm crank, but I'm staying NA, would you recommend the JE pistons and that Ottoco 86mm MLS Head Gasket?
What about rods?

[downforce22]

I'm building an M20 stroker with 86mm crank, but I'm staying NA, would you recommend the JE pistons and that Ottoco 86mm MLS Head Gasket?
What about rods?

I have had good success with the JE pistons ordered from RaceTEP but I did have one break somehow. The ottoco seems good if you can find it anymore, VAC might be the only one for 86mm bore headgasket. The 86 mm crank has larger crank counterweights so they may not clear the block. I'd run stock rods since they are strong and cheap, but my current engine has Eagle H beam rods I believe at 135 mm in length.

86 mm x 86mm would be a square engine. I believe the s50 crank is actually 85.8 which would put you at 2990 cc with the 86mm cylinder overbore.

[jeenyus]

love it. congrats.

[digger]

I'm building an M20 stroker with 86mm crank, but I'm staying NA, would you recommend the JE pistons and that Ottoco 86mm MLS Head Gasket?
What about rods?

Molnar 135mm rods are good and cheap will be machined properly from the box etc they also provide the best clearance of all the rods you'll see. best BFYB is probably OE 24V rods though

[downforce22]

Today was our first 90 F day this year and I spent lunch driving around for my first high temp testing with the car.

At cruise my IAT senor after the intercooler was reading ~100 F and after a quick boost run would creep up to 110 F.

I turned the car off and the intake heat soaked to ~130 F. Even after idling that started to drop back to 110 and then went lower as I drove. Ambient temp was somewhere around 85 F. I had guessed on my MAT based ignition retard and adjusted them slightly.

Here is my current MAT adjustment,
I may need to move the 120 up 5 F or so but it is decent for now until i do some more testing.


I also looked at the gauges in tunerstudio and wanted a more convenient gauge setup that I can glance at to see temps, pulsewidth, and ego correction as well a few other things to monitor. I stole some of this from my brother but here is my current dash that I see while tuning. i'll probably change this again but its got most of what I look for when tuning.



The last thing on here is using the Virtual Dyno software to see what kind of power i'm at. I made a two runs the other night but I kept hitting boost cut as my boost crept up so it skewed my results and i can only map a portion of the rpm range. Anyway I used 0.35 cD for the e30, 22 ft^2 frontal area, tire size of 205/50/15 and weight of 2700 lb with another 135 for me in it. I'm not sure how accurate this is but intake temp was 65 F and barometer was 80 kpa and this shows a run in 4th gear and a run in 5th gear. Both are close and have a significant torque figure and show my boost creeping up to 8 psi. I may have to try this again somewhere that isn't slightly uphill and increase my boost cut to see how it changes. It might boost creep higher as the rpms climb. One of the runs is the datalog shown in my last post.

[tschultz]

How fast is 4000rpm in 5th gear?? That had to be an open road!

I'd investigate your AFR table or add some fuel in your VE map so your mixture doesn't move towards lean like you are above 3500rpm.

I do think the variation between the two graphs is MAT density table settings (being leaner in higher temps.). You can obviously use Virtual Dyno or MegaLog viewer to see if AFR's are appropriate for the given ambient temp. And adjust that temp value correction to bring the graph either up and down.

[downforce22]

Yeah the undersize tires limit speed, but from this calculator: http://www.apexgarage.com/tech/gear_ratios.shtml
4500 rpm in 5th puts me at 105 MPH. I'll add some fuel up top after figuring out the autotune from megalog viewer.



I was looking at Lucifer's Hammer thread and it got me to revisit my engine specs to see how it compares to that one.

http://www.mye28.com/viewtopic.php?t=26880

This ended up with the 94.36 mm bore and the 95 mm stroke.

Yah, I know, some guys have gone out to 95 mm+ on bore diameter. IMHO, this leaves very little material between the cylinder walls. Keep in mind the S38 cylinders are 100 mm center-to-center. Go to a 95 mm hole and you have around 5 mm of material between the bores. So we stayed as thick as we could in the interests of strength and durability.

Knowing that the B38 blocks have a reputation for less-than-bulletproof strength, we also made te decision to give up some measure of top-end/high rpm output for engine longevity. While the motor can and will certainly turn 7000 rpm, the redline has been set at 6300 rpm.

Using the formula that max RPM is: 600,000/stroke length in mm, we get 600,000/95 = or 6315 rpm. Keep in mind this was built as an endurance motor, and I fully expect to see 120,000 miles (200,000 km) out of it.

In the same vein, 95 mm is probably on the long side for stroke. Rod length is 141 mm, so the rod-to-stroke ratio is 1.48.

The Big six (M30/S38) has 100 mm cylinder spacing, the M20/S50/S54 has 91 mm spacing.
With a 94.36 mm bore that leave 5.64 mm wall thickness on Lucifer's Hammer.
Lucifer's hammer has a Rod length of 141 mm, so the rod-to-stroke ratio is 1.48.

I'm running 86 mm bore with a 5 mm wall thickness on the M20B31. I'm running the 89.6mm m54b30/s52 crank. Using his formula 600,000/stroke length in mm = 6696 RPM rev limit based on crank stroke. My engine has rod length 135 mm, for a rod to stroke ratio of 1.506. Not sure rod ratio is really all that important.

I've got my revlimiter set to 6300 but the engine only makes more power up high due to boost and hits peak torque near 4500 rpm. I'll have to try another datalog. Revving higher on a stroker engine like this doesn't really gain much when you have torque down low that you aren't taking advantage of. Obviously this engine isn't a 'high hp' car.

[downforce22]

I had been on the lookout for some body panels for a while knowing the rust on the car was getting worse as I drove it over the winter and in the rain. When I drove it to moab, dust from the dirt roads made its way into the cabin. I figured it was coming from behind the drivers door where I could see some daylight and hear some road noise in the cabin.

A while back I was able to plasma cut a quarter panel off of a late iX. After that I found a rear panel listed on ebay for an early model car. I contacted the seller and was able to get him to cut a section from the left rear license plate light to around the corner where I had some rust bubbling. With those 2 components I dropped them off to see if they could be used to repair the damage. The body guy I know had some tie in his calendar and his lift open so I decided i might as well get it fixed. It needs to be fixed eventually and i figured I might as well have it done with a chance to have it back together before 2017 Drive 4 Corners and look half way presentable without rust holes through the body.

Here are some photos after he got it on the lift and took the flares off. The thick paint under the rear tail light and red primer points to a previous incident on the left rear corner. The sunroof drain did not drain outside the car, but rather into the driver floor jack fender wheel which may have been the cause of the rust in that area. If you don't like seeing rusty e30s, avert your eyes!

Here is the panel I got from the us spec ix set next to my car. It doesn't look that bad, right?















Yeah, it's pretty bad. Remember that road noise I was talking about? I think I found the problem... My guy will have to fab up the driver floor jack area from scratch because I do not have a replacement section for that, but luckily that will all be covered by the rear early model iX fender flare. Assuming the repair gets done right, it should be looking good and i'll have the paint matched close enough. It will still look like a beater but if that fixed the rust i will be stoked.





Stay tuned. should be getting worked on the over the next 2 weeks.

[stonea]

Good luck on the rust repair! I hope to do the same to my ix some day.

[litu]

Wow, that rust...I also have coming to rust repair time