Messages (Become)

The post comparing the two are here.

http://www.m42club.com/forum/index.php?topic=18442.225

Take note of the comments and digest the differences between the two comparisons as they are not like for like or a true Dbilas vs RHD comparison.

The RHD kit is on a newer M44 engine with mild exhaust mods.
The Dbilas kit is on a 230,000km M42 engine with full exhaust and a road tune aftermarket ecu. The Dbilas kit was modified to a state close to the RHD.

As the owner of the Dbilas kit in this comparison, I would recommend the buying the RHD kit as it is ultimately closer to where I modified the Dbilas kit to be. Something (for me) the extra $500 would justify.

Hi,

Can confirm coil drivers are on the dme. I built a 4 channel driver using bip373 kits from diyautotune if 4 channel drivers are hard to get or eye watering expensive as they in my part of the world this ua an economic solution.

Matt

Let's hope the drivetrain losses are greater than the 15% I assumed Anyway I'm studying automotive engineering at the moment and we have a lecture and laboratory dynotesting at our school next thursday and I get to dynotest my own Z3 there! I will post the results here, and I could also ask the teacher what are the expected drivetrain losses with these kind of power figures and drivetrain! 

That sounds pretty cool! I'm actually really keen to see it!

One of the other members here, MLM actually posted  his dyno results - which are very similar to mine. The interesting thing here though is that he has an extensive list of modifications, including a custom tune.

http://www.m42club.com/forum/index.php?topic=18772.0

Now he is in a different country on a different dyno, however using this only as an indicative example you can actually see some characteristic differences between his setup and mine as well as it being interesting how similar our results are. He is using the Dbilas kit and a larger diameter exhaust with a larger airbox. His curve behaves exactly as I would expect, there appears to be less power down low, and less torque overall. Now that I'm so close to the end, I think I will send him a message to see how accurate the RPM readout is, and then plot his curve in excel against mine, it would be very interesting. Anyway, it would seem to indicate that there are probably about 25% drivetrain losses. Don't forget our gearbox was designed to cope with the much torquier 6cyl engines, so it is quite heavy.

If you can collect the RPM and road speed for your dyno test I'll plot your OEM against mine, as well as against my results. Again, it is only indicative but it will be interesting. It will make for a pretty chart!

Hi Lambertius

I am more than happy for comparisons to be drawn and am interested also in dyno overlays also. Despite our approaches we have not ended up in too dis-similar places. Re rpm plot I have no reason to doubt their accuracy but cannot say how they were captured.

My modifications are:
- ITB with home made trumpets and airbox much like yours in terms of mod style though with different details.
- Aftermarket ECU for future flexibility - tuned for everyday 96ron with longevity in mind.
- 2.5 inch exhaust with 2 mufflers and a resonator, not straight through though less torturous than stock.
- equal length headers, again home made. A bitch on RHD cars BTW.
- That's it.

The engine is a M42 (not M44 designed for more torque) of 1992 vintage with 235,000km on it so far from fresh. Its has had 'good' use all its life.

Im an engineer but not automotive trained and have no automotive support other than the internet.

Ive been on two different dynos which both read similar 87.5Kw as per your link and an 89Kw elsewhere with no changes in between other than dyno.

I plan future expansion with cams, bore, compression hence my design choices as im not in a position to redesign/change decisions made today.

A good project you have undertaken - well done.
 

From measurement I recorded.

Piston 7.5cc
Head 34.5cc
CR comes out at 9.87:1


Make sure your adding and subtracting volumes appropriatly for deck heights and dishes etc. Messed me around for a while. For my theoretical combo I use stock rods, pin diameter, HG, Crank, bored but not decked block and get 11.5:1 with the nissan piston and 1.2mm squish. Just trying to decide if I decrease the squish to .8mm or not with some block machining (or thin HG) and go for 12:1.

According to the excell spread sheet i just whipped up...

If .65 above deck and flat top you get ~ 12.1:1.  Squish distance on 1.7mm HG = 1.05mm
If .9mm above deck and flat top you get ~12.5:1. Squish distance on 1.7mm HG = 0.8mm

Machining to reduce compression would take a fair bit of meat off the piston.

Im was looking at a Nissan piston which gives 12:1. A squish distance on 1.3mm HG of .8mm  (86mm bore). To get 11:1, I need to gain 4cc in the chamber as i dont want to machine the piston.

Or

Stick with 1.7mm HG and resultant 1.2mm squish and 11:1.

Do I shoot for a better squish of .8 but have to machine somthing to drop CR to say 11:1 OR go the easy way of 11:1 CR and wide squish gap with no machining. What i have learnt so far im not sure if i want to trade off squish gap...

Takes alot of math and playing with ideas to get numbers which sound right...

 

Just a thought. If you skimmed the block 0.65mm and kept everything else stock. You would get a squish of 0.8mm and 10.7:1 CR...

If my maths is right, it would be a relativly cheap rebuild option assuming you could get the chip to suit. Would require piston to valve checks but may yeild some HP otherwise missed out on.

I think the benifit of squish applies to any induction type maybe more so in a turbo where detonation is a real problem. 

Modded turbo engines with thicker gaskets would indeed upset squich to achieve a lower CR. Just happens to be the easiest way to reduce cr is a thick head gasket.

found a good explanation in this thread http://forum.9000rpm.co.za/viewtopic.php?id=5272

These guys say 0.7mm is good on a 4age.

Worth cosidering when building for sure.

Athena do a 87mm gasket, http://www.rallyshop.it/index.php?main_page=product_info&products_id=22065&language=en  bit pricey but another option.

If the m44 is 86mm and 1.7mm stock thickness, you would want to ensure the piston is below deck height to go bigger or equal bore.

 I suspect the .15mm above deck the m42 uses is to achieve a 1.55mm squish clearance (Which acording to my reading is quite wide already, 1.2 is more ideal). This is somthing you loose if you have to stay below the deck to avoid the HG eg 1.75mm+. Squish/quench helps burn which helps power at lower rpm which is useful power.

Not sure if the numbers there are 100% but be aware choosing a piston to not hit the HG means your trading off another aspect of design which make power too.

On a stock ECU you need the AFM, There has been no sucessful conversions to non afm on the stock ecu to my knowlege using MAF and chips etc though there are some working on this.

To throw out the AFM 'just' throw in an aftermarket ecu and retune from scratch.