engine and drivetrain Tii Rough Idle And Mixture Question

[otisdog]

So after reading the Technical Correspondence article - am I right in assuming that if you add only higher compression pistons, the Kugelfisher will be fine in its' stock form? Are these pistons still available? Thanks

 

[kaptanoglu]

So after reading the Technical Correspondence article - am I right in assuming that if you add only higher compression pistons, the Kugelfisher will be fine in its' stock form? Are these pistons still available? Thanks

 

That is the conclusion that I came to as well.  Top End Performance (FAQ sponsor) who built the motor used JE pistons w/ 2mm overbore and 10:1 compression.  I do not know if 10:1 pistons are available from BMW.

 

J

[bnam]

One caution though -- several Tii owners have posted about difficulty in getting the KF system to enrich sufficiently at WOT/higher rpm.  Maybe Ethanol in fuel related or worn KF pump related, but high compression + leaner mixture might not be good.  So, renewing the KF system is probably also warranted.

[kaptanoglu]

One caution though -- several Tii owners have posted about difficulty in getting the KF system to enrich sufficiently at WOT/higher rpm.  Maybe Ethanol in fuel related or worn KF pump related, but high compression + leaner mixture might not be good.  So, renewing the KF system is probably also warranted.

 

Understood and agreed (and I did have the KF rebuilt).

 

I will continue to be nervous about this build until it runs, but took some small comfort in the attached graph (pulled from 2002tii.org).  It shows that the cone in the 74 tii (the V6, which I have) is a bit richer at WOT than the pre-74 pumps.

 

I will do a full write up in a couple of months when I have the car, the AFR and a dyno.

 

J

 

[SydneyTii]

BMW dont do the Tii OEM pistons anymore, but Ireland etc will supply pistons and think Jaymic in the UK has some Tii ones as well, 10:1 compression is nomal euro compression for a good Tii engine over there (from memory) I use a bit of valve saverin mine and it seems to run better. Everyone who I know who has had a rebore to small oversize ha had no issue with the pump being able to fuel the motor, I dont think the tolerance was that close. From a few of the posts it does sound like the ethanol issue is a bit nasty for you guys, we can still get 98ron in Aus and mine loves it :-)

[otisdog]

thanks for your responses...this place is such a trove of info.

[thehackmechanic]

Just FYI... if you search here on the FAQ, you'll also see people's opinions that, after 40 years and either no rebuild or a questionable one, the difference between the delivery curves of the early versus late Kugelfischer pumps is not thought to be significant, and that for all practical purposes, the pumps should be considered interchangeable. I'm not saying they are or they aren't; I don't have the expertise to know. I'd imagine it's one of those "all other factors being equal" things, where all other factors are NEVER equal...

[kaptanoglu]

Just FYI... if you search here on the FAQ, you'll also see people's opinions that, after 40 years and either no rebuild or a questionable one, the difference between the delivery curves of the early versus late Kugelfischer pumps is not thought to be significant, and that for all practical purposes, the pumps should be considered interchangeable. I'm not saying they are or they aren't; I don't have the expertise to know. I'd imagine it's one of those "all other factors being equal" things, where all other factors are NEVER equal...

 

C'mon, Hack, I want to believe that Sputter is going to run great.  I am not sure who Steve (at Top End Performance - FAQ sponsor) used for the Kfish rebuild, but I will give them credit for having done a good job.  In my case, it we have a rebuilt pump, cleaned injectors, recurved dizzy (by Advanced Distributors) and a hot (hopefully in a good way) motor.

 

I am picking up the car in two months, but should know if it will run well with the current set up in under a month.  My fall back will be reverting to a stock cam, as everything else should be fairly benign.

 

[02fanatic]

Why modify a tii to such extremes which is not designed for? A properly set up tii engine (meeting factory specs) is a beauty and should not be messed with. Sorry but I had to.     

 

I agree totally!!!  Why mess with something that is PERFECT to begin with?  This has been an interesting thread though.  tii's are awesome, especially considering that a well tuned stock tii will get 30mpg all day long and cruise at 80mph with power to spare...and these cars are over 40 years old!

 

I'll always cherish the days when Michel Potheau advised me when I was restoring Hugo ('72 tii #129) over 10 years ago....resources like Michel are sadly being lost!

[kaptanoglu]

I agree totally!!!  Why mess with something that is PERFECT to begin with?  This has been an interesting thread though.  tii's are awesome, especially considering that a well tuned stock tii will get 30mpg all day long and cruise at 80mph with power to spare...and these cars are over 40 years old!

 

 

This is going from a tuning discussion to a philosophical debate, which can be fun, too.

 

While I agree that a perfectly stock tii is a fantastic, remarkable car, to me PERFECT is relative.  To me, the tii, along with all other cars (save the new McClaren PI) has a host of compromises, and each of us, when working on our cars, make a number of decisions about the compromises that were made by BMW 40 years ago.

 

 

On Sputter (a '74 tii), we took the following approach:

1 - We wanted it to look stock, but decided to make it look like a stock European tii (those 74 bumpers are ascetically challenging) 

2 - We had to keep the Kfish.  That defines a tii, and, while as charming (and reliable) as an old automatic watch, is crucial to the car

3 - We wanted it to perform a little better than stock when driving (a little more power, a little less body roll), but not like a race car

4 - We wanted it to be usable as a daily driver in Houston, TX

 

On the third point, this list is full of commonly performed upgrades that make these cars a little more PERFECT, from Getrag 245 5 speeds (which we did), to stiffer springs/bars (which we did, though softer than most, going with the ST springs and bars), to LSD diff swaps (which I will do later myself) to engine swaps (which I might have done if it wasn't a tii), to wheel swaps for wider tires (which I haven't done.  Sputter rolls on steelies).

 

My question to TEP was "how well can we make a tii engine run?"  10:1 pistons seem like a no brainer, since that's what came on European tii's (since the Germans didn't trust us at the gas pump), as did a bit of porting and polishing (even if that doesn't help), and headers (same).  I suspect that if the Kfish were more widely adjustable, 75% of the tii owners on this list would have put in a hot cam as well.

 

On the last point, PERFECT is a function of Germany vs. Houston and the passage of time.  To make the car a reliable daily driver in Houston, we:

- Epoxy primer coat (these things are rust buckets otherwise, this "California car" included.  It rains here, and this isn't a trailer queen

- Pertronix (which, I suspect, most folks have done in lieu of points)

- MSD (better cold starting, better idle, I am told)

- Bigger radiator

- Bigger alternator

- Very, very non-stock A/C (though it will look stock inside the cabin)

- Modern (but very discreet) audio

 

We'll see soon enough whether or not we were able to achieve all of these objectives, but I am hoping that at MidAm you have a look at Sputter and think, "It looks like a bone-stock Euro tii, but a little more perfect," and hopefully it will run that way as well.

 

J

Edited February 22, 2014 by kaptanoglu

[classicman]

To get back to my original thread, I have finally fitted the AFR gauge to my car, and what a pleasure!!!! I was running hugely rich, and have had to take the verboten screw in by two full turns to make any form of difference.

The car is running much better now, but I have reached the end of the adjustment on my verboten screw and she is still running rich. At full bore acceleration thought the gears, the reading comes in at a shade over 13 before she comes onto the cam, the reading drops to about 12 when on the cam. From reading in previous threads, I am aiming to get to about 13.7 on the gauge, is this correct?

So how do I weaken the mixture further if I've run out of verboten screw? She starts easily and idles lumpily at about 1,000 rpm. I'm not entirely convinced that I am getting full power on the cam though.

Any thoughts?

[PaulTWinterton]

Somebody please correct me if I'm wrong.

As I'm sure you know, there is also the KF linkage intermediate shaft adjustment. While setting up the linkage (pinned), you can partially cover the 4mm hole (at idle) in the tuna can with the cam, as opposed to the cam resting (pinned) on the edge of the hole. The more it covers the hole the richer the mixture throughout the range. Therefore, check your cam position at idle and adjust for leaner or richer running.

Interestingly, I believe most of us have lean running problems. You have rich running problems. I think with more adjustment, you'll be fine.

I'd start by resetting your KF to where it was originally. Then adjust your intermediate shaft and tuna can air screw. Once you've adjusted those to best settings, then re-evaluate the KF settings.

[classicman]

Ok, so after further investigation, I have found that the cam that fits at the bottom of the KF pump (where you set with the 5mm rod for idle and full throttle conditions) had moved and thrown my settings out.  That also explains why I wasn't getting full throttle and the car felt like it wasn't coming onto the cam properly. I took the pump off the car and found that the splines on the cam were worn smooth.  I fitted a spare one and reset everything on the bench before putting the pump back in.  Got her idling fairly smoothly at 1,000 rpm and 13.0 on the AFR, so looking good.  Its been raining though, so I haven't been able to try her on the full throttle again, but I'm hoping I've solved the problem now.

 

I don't know why I didn't fit an AFR before, it makes science out of guesswork!