1986 325iX 3.1L Stroker + Turbo

[downforce22]

I havent pulled the trigger on the turbo cam but have been dialing in the tune. Here are some screenshots and general notes about the tune that i have done lately.

I took the car on a fall leaf cruise and made a small video. I forgot how fast this car is. We staged at the local BMW dealer and had a few friends show up with an e30 m3 and others. I dropped off the group with other plans so these are the best photos I got. Enjoy the video.

20200926_075409 by t sz, on Flickr

20200926_082956 by t sz, on Flickr

20200926_101835 by t sz, on Flickr

20200926_101856 by t sz, on Flickr

I didn't like the start up sequence so I have adjusted the enrichments and idle settings. First up is WUE which needs some more fuel at colder temperatures probably but is getting closer.

wue by t sz, on Flickr

My current mat table, not sure how accurate it is but it is what i am using.

mat air density by t sz, on Flickr

Idle startup is based on coolant temp and seems pretty decent so far. Based on coolant temp.

idle cranking duty by t sz, on Flickr

Target idle settings

idle target rpm by t sz, on Flickr

Closed loop idle settings seem alright right now but still some work to do.

closed loop idle by t sz, on Flickr

closed loop idle initial settings are getting there too.

cl idle inital by t sz, on Flickr

The EAE is tough to dial in stationary due to the varying fuel map values so I have been adjusting based on datalogs. i also seems tps is better so it is more tps biased.

eae by t sz, on Flickr

I smoothed out the afr targets.

afr by t sz, on Flickr

I smoother the fuel out but it is still a little rich in some areas. you can see the power band of the engine from the shape of the table.

fuel ve by t sz, on Flickr

Here is my current spark table. I added some timing, about 2 degrees at 80 kpa which is atmospheric where I live. It seemed to like that and didn't increase the likelihood to knock due to 0 psi of boost there. I added 0.5 degree at 105 kpa. I smoothed out the ramp going up to 2250 rpm which meant about 2 degrees removed. I am not sure whether that helped anything or not.

spark ignition by t sz, on Flickr

Here is pull in 5th gear showing full throttle from 1800 rpm to 5000 rpm in 5th gear (40 mph up to about 115 mph with these wheels). it goes rich due to my fuel map and eae but then stabilized at 12 afr as it passes through 100 kpa and up to 120 kpa or 6.5 psi. Temps were cool in the 40s so I felt comfortable doing this. Advance ramps down from about 21 degrees to 19 degrees at 124 kpa

5th gear pull 1800 rpm to 5000 rpm by t sz, on Flickr

This engine runs pretty good in the mid range. I have street tunes this whole tune and it is decent. There has been a problem with cooling. The blower would go cold for a bit and coolant temps would rise briefly to 205 or so. I found a small leak at the firewall to the heater core so I replaced a hose clamp on that. There was also some residue on the driver frame rail area by the abs system. I tightened the hose clamp for the late model reservoir and test drove again. Still leaking and low fluid. So i changed reservoir caps to a 200 kpa one and same thing (pull above getting to 213 F). So I believe it is the reservoir and I ordered a new one. Hopefully that will help fix that problem but who knows.

I am trying to iron out these details and looking forward to driving it more once I get the cooling system figured out.

[digger]

Z45 is a fairly mild can for a 3.1L but a decent step up from stock. For a turbo unless you have a really restrictive hot side ( high exhaust pressure) a NA cam even fairly aggressive works ok so don’t feel like you need to limit yourself to a turbo specific cam.

[downforce22]

I did some more digging and found some more info on cams on here. Putting it here for reference.

https://www.r3vlimited.com/board/for...9-cam-question

To explain this fully, it would be a long post and in a place not many people would see in the bottom of a thread. Do some reading up on dynamic compression to get a good grasp on it. Just be aware some of the info out there is pretty dated, but it really helps visualizing what I meant by matching.

In short the cam overlap (both valves open simultaneously) can help or hurt depending the the intentions of the engine. A lot of duration/overlap (can be lower duration and tighter center lines too) hangs the pair valves open longer, allowing intake gasses to pass into exhaust without combustion, and also exhaust pulses to revert to the intake.

Now if you have a really high CR with a low overlap cam, you are trapping more mass (increasing dynamic CR) and it gets to a point where the fuel mix will pre-ignite from pressure no matter how little timing advance. In a lower compression you have the opposite. Too much mix is being expelled and will get to a point, the engine won't even start - the flame front will just go out the exhaust instead of pushing the piston down - path of least resistance.

So, in a running engine things change as RPM increases (dynamic CR) due to all kinds of variables. Such as back pressure in the exhaust (high RPM, running condition), a long duration cam won't bleed as much as if cranking to start, there's already pressure in the exhaust helping it stay in the chamber.

With that in mind, you can see how cam specs will kind of indicate the temperament of your engine. Low compression takes more RPM for a big cam to reach the point where it's most efficient. Many times people will over cam the engine and all the real power it "could" make is outside of usable range. When we design custom cams for the domestic makes, we try and walk that fine line of too much trapped mass (dynamic compression) so that as much of the combustion/flame is pushing on the piston as possible (maximizing VE). Over cam-ing them sure does make a cool idle though lol - just don't expect to have any brake assist or crankcase ventilation since vacuum won't be there. We actually sell a "thumper" cam people like because has a crazy sounding idle, but doesn't make as much power as the others since the peak power is above the redline.

It wasn't an m20 and has a fair bit better combustion design, but we had a client with 13.8:1 compression running pump fuel (93 octane) with a matching cam (stock engine was 9.6:1). He is in FL, so we don't have any emission standards and never tested his, but based on remote tuning for other clients with a little less CR, his could be made to pass (specially if EGR was retained).

you CAN NOT make very good VE without a fair bit of overlap, this includes at low rpm like 2500rpm. but it is a double edge sword. while it is working for you it is great but when it works against you it is a nightmare because of the effects of reversion.

while an exhaust is scavenging you can almost not have too much overlap, however on a street engine you cant design an exhaust that scavenges across all rpm from idle to redline at all load points so you need to compromise.

if the rest of the engine isnt designed for the rpm of the engine then changing one part of the system wont produce the results you expect. the inlet, cam head and exhaust and bottom end shouldnt be considered as separate systems

I have found, though, power comes from the top end. As long as your cam is designed around the CR/RPM, the rest is just how efficiently you can move the air in and exhaust out.

Ironic you mention overlap. It is believed that little/zero overlap is optimal for turbo, which I never believed. Had an order for a 3.8l Camaro a few years ago and ran many simulations through Dynomation to come up with a great cam to match the highly modified head/intake we worked over. The engine builder/tuner (assembler?) argued tooth and nail the cam was "too hot" with ~58° lap. Stepped it down just a bit per the client request, engine builder still was hesitant. Long story short, they couldn't believe they gained so much power. Instead of being 400whp@22psig, they were well over 500 at only 14psi. Old heads were "ported" by another company (no numbers or bench proof), and was running their shelf "turbo cam".

https://www.r3vlimited.com/board/for...es-and-rockers


I am leaning toward the longer duration more overlap and modified LSA Z45 turbo cam.

Some more info:

What exactly is a stroker cam? According to Comp Cams' lead cam designer, Billy Godbold, "The piston velocity in an enlarged stroke engine is greatly increased, resulting in an intake charge event which continues even past the point of Bottom Dead Center (BDC)."

What this means is that the long stroke increases the acceleration rate of the piston down the bore (relative to a shorter stroke). The draw on the intake charge from a stroker motor is so strong that cylinder filling actually continues to take place past bottom dead center. The XFI intake cam profiles feature late intake closing points to take full advantage of the extra filling offered near the end of the intake stroke. In addition, the exhaust valve is opened earlier to help reduce some of the pumping losses associated with the increased stroke.

http://www.mustangandfords.com/how-to/engine/mmfp-0609-stroker-cam-comparo

[downforce22]

So long time, no update, I have been preoccupied with other projects. But it is time to start getting back to this car. The driver window wasn't going up and down fast enough so I tried a different motor but it didn't solve the slow speed of the window. I found some crank windows rails and decided to swap those in. So far I have just changed the driver side and need to swap the passenger side too.

In the mean time I was thinking about how this engine drove and realized the stock camshaft and 885 head is probably severely limiting power. I had skipped over that phase of the engine build and have been wanting to learn more about camshaft and valve timing. Sure the m20 is old and doesn't make much power, but that isn't the only reason we learn and work on cars. I was talking about this with a friend who suggested I should add to this thread. Even with the broken piston, and the body work I have some hands on knowledge that would have cost the same from a automotive school or class.

Anyway, I have been looking at some engine specs, from the M30 in the lemons e28 I will be racing in this weekend, to the evolution of the S38 in my other project, and back to the m20. They are similar enough engines and a good starting point for comparison. Ultimately what I failed to realize when I started this build is that the cylinder head is very important to look at when putting the whole system together. Sure, displacement is very important, but the camshaft and head change the necessary variables that either make for a great engine or an average one. The two variables I am looking to solve are the following:

1 - Powerband
2 - Boost Creep/ Detonation

The car has loads of torque down low but starts to taper off around 5000 rpm which is just when the fun gets started. I'd like to shift the powerband higher. I believe the extra displacement is being choked off due to the dynamic compression ratio of the stock cam's powerband. Also, for boosted engines, camshaft selection more or less comes down to overlap, intake valve closing time, duration, and valve lift. In a turbo engine as overlap increases, the intake gases in a boosted engine can blow through and out the exhaust valve. Valve lift is dependent on the cam design. Cam Duration would affect overlap. Therefore the most important event is going to be when the intake valve closes in relation to the exhaust valve opening. If it closes early we reduce overlap; if it closes late we increase overlap. As we increase duration we increase overlap. Air could blow through the engine out the exhaust, or with too much back pressure, reverse from the exhaust back into the intake.

https://www.tildentechnologies.com/C...rformance.html

The effect these parameters have on performance is easily understood if you remember that intake closing is the most important event. Because of gas compressibility and inertia, closing the intake valve sooner produces more low end power and torque and less power at high RPM. Closing the intake valve later produces more high end power at the expense of the low end. This explains why an increase in the intake valve duration moves the power band to higher engine speeds. When the cam is advanced, the intake valve closes sooner, so you get more power at the low end. Reducing the lobe separation angle also causes the intake valve to close sooner, so you again get more low end power.

This is where things get unclear for me. Since static compression wont change, the only things we will be doing is increasing lift, changing duration, and changing overlap. With my engine being a 3.1L and a 9.5:1 CR I suspect my dynamic compression ratio is higher causing some higher likelihood to detonate. If I can increase overlap that should decrease the DCR and a longer duration will allow the engine it breathe more air. Either way it sounds like I want to increase overlap, increase duration and increase lift to shift the powerband higher. This of course causes problems as increasing duration almost necessitates increasing overlap which could be counter productive due to air blowing out the exhaust. But at BDC and TDC the piston is not moving very fast so overlap is acceptable at both of these times as long as you have piston to valve clearance (at TDC).

Looking at camshaft timing this is what I have found for the M20 stock 885 'K' cam. It is more or less matching up with multiple forum posts. Plugging in to the calculator it shows the overlap and timing of valve events.
264 duration
lift ~10 mm
115 LSA



Exhaust Open: 67BBDC
Exhaust Centerline: 115BTDC
Exhaust Close: 17ATDC
Intake Open: 17BTDC
Intake Centerline: 115ATDC
Intake Close: 67ABDC
Exhaust Area: 32.8
Intake Area: 32.8
Exhaust/Intake Area Ratio: 1.0 : 1.0
Overlap: 34
Overlap Area: 1.3
Overlap/Total Area: 1.9%

Using this handy tool I got the data above and compared it to the two options I am looking at as well as the stock one.

https://mgispeedware.com/camshaft-calculator/

https://www.summitracing.com/newsand...ing-calculator

The options I was looking at were the tried and true ENEM Z45 Turbo Cam, or a dual pattern like digger's recommendation for 2.8/2.9 strokers the 284/272. I also found the catcam turbo cam 270/249 cam* (might need cam wheel replaced). So I found this calculator to compare valve events on the different cams.

Anyone expecting to gain power everywhere from a cam should do some in-depth research into camshaft theory because unless you have a really poor cam to start with (BMW's aren’t poor) it won't happen. If you want to gain top end and midrange be prepared to sacrifice some bottom end that is the fundamentals of the airflow dynamics.

For a 2.7/2.8 a schrick 284/272 is a very torquey cam and would very work well it will make ~85% peak torque at 2500rpm but won’t be a huge top end screamer. A catcam 273 would be another option which is what the UK guys are leaning towards nowadays.

Essentially I am looking to increase lift, increase duration and keep overlap about the same as stock, but want to hear some feedback from guys like digger, forcedfirebird and other m20 gurus. I am leaning toward the z45 but want to learn.

It appears the intake valve opens longer and later on the schrick and the z45 which is desirable, but beyond that I am not sure what I am looking for. Obviously the schrick has more lift which could be problematic for the pistons I have.

[Mooms]

this car is rad

[tschultz]

Also got some audio in the D4C video :D

http://www.youtube.com/watch?v=VBXJXzvhWHs

[fiftytakedowns]

Im in Colorado Springs, take me for a spin!

Hah!

[varg]

I got mixed reactions at the meet, people thinking it was a hunk of junk until I revved it a bit and opened up the hood.

Yes, you stand out a lot from the crowd of plebs with cookie cutter Audis.

[downforce22]

So after the last failed attempt and the latest news about the cog railwayclosing causing trips to the summit to be only for handicapped/car seated children otherwise a mandatory shuttle, I decided to try for the summit again with the same group this past weekend. We made it to the summit. I could feel the power loss up above 13,000 ft and my BOV wouldn't open as easily at that altitude so I got some compressor chatter. Needless to say the car performed well and the guy behind we asked what was under the hood because he couldn't keep up out of some of the corners. Enjoy some more large photos.



























The more photos i take, the more the edges of the front bumper not lining up bother me so I will have to see what i can do to mount those correctly. Not shown is me installing some wheel studs in place of the lug bolts. That should help make my wheel changes go faster. I also fixed the passenger city light, as the wiring was pinched in the headlight bucket. With the way my keyless entry is wired up and how I used the old running light wiring to power the city lights, now when I lock or unlock the car both the rear running lights and the front city lights in the euro smilies flash which is pretty cool. I also had picked u a cool grille badge last summer and I finally installed it on my grille. Check out both in this picture.



And a clickable image showing how easy it is to daily drive. Up next is fine tuning my acceleration enrichment and MAT based timing retard.

[tschultz]

I don't recognize that parking lot at Glen Cove, maybe I just haven't been up there in a while!

Nice photos... sounds like it was fun. I'm not sure how you can compensate besides restarting the car at altitude. I was pretty happy with my last drive via Mapdaddy when I drove to Estes Park up to 8000'. Still was working on the tune in conjunction with MAT, as they definitely can influence each other.

I wonder how your car would look with chrome bumpers and beltline trim, but blacked out window trim. Either way, looks good.

[downforce22]

My buddy started a local group since he is into Audi's and since I showed up to the last group meet in my 318iS, this time I took this car. The event was a group drive up Pikes Peak along with an Audi group from Denver. My car didn't really fit in but I had a good time taking photos. Unfortunately we hit some weather at Glen Cover (11,000 Ft) and they closed the road to the summit for the rest of the day.









10000000_629649720720300_5098337909354790912_n, CLICK FOR VIDEO












Then we got some dippin dots style snow. Good thing I put my snow tires on that morning and wasn't running autocross slicks!







You can see the cold side of the hood got some snow on it while the turbo side was all melted.







Soon the dippin dots snow slowed, then turned to a cold rain and we decided to call it and make the trip down to a local brewery for the storm to pass.


My friend asked what the Euro plate meant and said he really liked it after I told him. He drives the black Allroad wagon (2.0 Turbo)



After that, a small group of decided to take some more pictures.













I did a little exploring after trying to grab that last picture and took a couple more.



All in all the car did good up to 11,000+ feet. I do have a slow coolant leak and the exhaust rattles on the rear subframe so I have a couple more things to fix. The passenger city light housing doesn't work but I have a new one to replace it. My tune needs some work as it was pretty rich going up and decently rich coming down until I restarted the car. I got mixed reactions at the meet, people thinking it was a hunk of junk until I revved it a bit and opened up the hood. One guy really liked the exhaust sound and said it sounded 'pure'. He also thought I was driving really fast which is a surprise because i was on snow tires and the car really leans and pushes wide when coming out of turns under power. I was considering a swaybar change and learned only the fronts can be changed to +1mm to the iX touring bar. Going to bilstein front struts might help but I haven't gotten around to doing that yet. I think I need to adjust my MAT curve a bit to come in at about 80 F, add a couple degrees of timing under boost and play with my AFRs to dial them in, 10/11 AFR isn't fun under part throttle.

Stay tuned for more updates.

[rzerob]

I am getting ready to do a restoration on my ix. I wish I had an early model every time I see your thread. I will most likely start a thread of my own probably in the middle of the summer. Keep up the great work.

[jeenyus]

very cool.

[downforce22]

Thanks bradnic. Here's a couple from the front.

[bradnic]

such a crazy rare car
so great to see the rust repairs and federalized side markers gone