'68 Morris Mini with 1310cc A+ Engine

[jb007]

Around 4 years ago I started on the journey to convert my Australian 1968 Morris Mini fitted with a later 1986 A+ 1310cc engine to TBI. I started this conversion partly because I liked tinkering with electronics, but also because I needed a project to help me drag myself out of my Major depressive episode that was hindering me gaining employment. I'm happy to report that I conquered all three!

Initially I started with a MS2 and then upgraded to a MS3 ECU, and I used my current HIF44 SU carburettor as the TB using a Patton Machinery adaptor that uses a Rochester fuel injector running around 12PSI. Some people refer to this system as a wet manifold system. I was very aware that the A series engine has an inherent problem with charge robbing due to it's Siamese ports, but I was, and still are not, looking for the ultimate as I believe the gains for the outlay are not worth it. I'm also using wasted spark using a ford coil ignition pack.

The car is at the moment undergoing yet further changes, I will be converting to using a Bosch HFM5 MAF, partly because of the good results a few members are reporting here.

I originally documented the build on two different Mini forums in Oz, but recently have moved it with some editing to my Blog http://www.jamesobartlett.com, so If you want to know more about my conversion, please have a look and feel free to comment. Also thanks to all on this forum for helping me with my queries.

Jim

[DaveEFI]

Great stuff. But was wondering what extra you get from an MS3?

[racingmini_mtl]

I don't know if you've seen what some guys in the UK have done but it would be worth a look at the turbominis.co.uk forum. And you might want to reassess your view that the port injection setup is not worth it.

I had a look at your blog and was interested to see that you use the cheap SSR in a PWM fuel pump setup. So there is no heat or control issue using 125Hz PWM?

Jean

[jb007]

Thanks Jean I didn't mean to offend you. What I meant was that for the extra power and drivability gains, the extra cost of ditching my TBI setup and going to two injector semi-sequential, (plus extra wideband?) to me would not be justified it at the moment. My income has been reduced to ~1/3 of what it previously was so I have to watch pennies very carefully!

I have also followed the threads on turboMinis and it was these that inspired my build. Maybe a future stage III build after I do the MAF thing!

Jim

[racingmini_mtl]

Jim,

I'm not offended at all. I was only pointing out that there are gains and I wasn't sure how aware you were of the potential. However, you're the only one who can say if it's worth it for you and from what you say, what you have if likely a good compromise for now. I'm sure it's a lot more tunable that fiddling with SU needles and springs.

I look forward to see your results with the MAF.

Jean

[jb007]

I had a look at your blog and was interested to see that you use the cheap SSR in a PWM fuel pump setup. So there is no heat or control issue using 125Hz PWM?

Sorry Jean, I forgot to ask you what you mean about the SSR. I haven't used it yet, or even setup up on the bench yet. It does have a metal backing plate/heat sink. Is it a crap SSR, if so I'll get another.

Jim

[racingmini_mtl]

I don't have actual experience with those SSRs but I have read some positive and negative things about them. The issue is that with cheap products like those from Ebay (which I assume is where you got this one) you don't always get the same thing even if they look identical. I have also seen that they may not like a 125Hz PWM signal as they have a longer switching time than you'd need for that. You may want to limit it to 100Hz or less but then the pump may not like it.

As I said, I don't have actual experience with them but you can give it a try. It will either work or not but it may heat up like crazy if you're switching it faster than it can be. So watch for that when you try it. Also make sure you use an isolated signal because if it fails it may backfeed 12V to the input so that would not be good for the CPU.

Jean

[jb007]

Thanks Jean.
I've been doing a bit of research (should have done before buying!) and your right not all SSR's are equal. Some have turn on times in the multiple milliseconds range. These are supposed to be 0.5 for both turn on and off. Apparently some pump motors react better at higher frequencies ~ 1KHz and above so most SSR's would be useless.

I think I'd be better using a N channel MOSFet say something like this: http://www.jaycar.com.au/productView.asp?ID=ZT2466 What do you think Jean? Would I be able to just drive its Gate with say a 1k Resistor from the +5V O/P from the MS3.

Thanks for your advise... PS When I write this up on my Blog is it OK if I reference your WEB site?

Jim

[racingmini_mtl]

It's usually better to use a FET driver with most FETs. You can use a smaller gate resistor which means a better switch on/off time and significantly less heat.

And yes, you can reference my website.

Jean

[jb007]

Jean, would this be better, I can make up a circuit, or maybe even side MS3. http://www.msextra.com/forums/viewtopic ... er#p423662
What do you think?

I also note that the max freq that the PWM Fuel Pump in MS3 can go to is 250Hz... how does one determine the best operating freq of their pump. Suck it and see?

Jim

[racingmini_mtl]

That would be a good circuit to use. As for the frequency, other than making tests to determine what the best one to use would be, you can either try to get information from the pump manufacturer or rely on what others with the same pump are using. But if the pump doesn't make too much noise, doesn't get hot and you can control the pressure as needed, there's a chance it is good enough.

Jean

[jb007]

Don't you ever sleep! I might go with this cct. My pump is the Rover SPI unit mounted in the tank, so it would be hard to test for heat other than feeling the tank after a prolonged period of time. Thanks for your time and input.

Jim

[jb007]

I just had an idea. If I can run water through the pump, I have a spare pump, I can set it all up on my bench and test it that way without sending the whole place up in flames.

Jim