Help Picking Target CR and Boost
Turbo Mini Forums

Hello,

I plan on building a turbo mini which I want to get to about 140hp max.

I have bought an exhaust manifold that will hold a T25 turbo, and a Metro Turbo Plenum

I want to keep the engine bay as standard as possible so if I don't want to use an intercooler - just the Metro plenum - what is the max CR and Boost you think I can aim for?

I found an older thread on this topic but it was about a 998 engine whereas I am using a 1275 +0.20 so not sure if that would change the target values.

I will be using an SW5 cam on the build and will have programmable ignition obviously.

Thanks for any contributions,
Nik

For the love of cars!!

With a decent cylinder head and build etc @8.6:1 comp ratio, I would have thought 11 psi would make 140 ish bananas. Need an intercooler at that boost

Edited by dazibee on 7th May, 2018.

Depending on the engine spec 10-12psi should make your HP target. Even on an efficient turbo you'd ideally want an intercooler at that kind of boost otherwise you're just throwing free power away. You'd also have to run a lower compression ratio and more ignition retard, lose, lose IMO.
If your dead set against an intercooler have you considered water injection ? This can be installed very discretely and is an excellent detonation suppressant.

Phil.

WWW.TURBO-MINI.COM

Thanks dazibee and Turbo Phil!

Phil what kind of CR levels are you talking about in the case I do not use any cooling method other than the plenum?

My only real concern with water-meth injection is that if I run out of liquid during a rally and not realise it I will be at risk of doing some serious damage to the engine. I will of course have oil temp/pressure gauge, water temp and I was even thinking of sticking a level warning in the container that will hold the liquid, but still the feeling of uncertainty will always haunt me..!

For the love of cars!!

intercooler, foolproof tech (almost)

You could tie the water injection system into your ignition system, or, more directly, intake temp. If you run out of fluid or the intake temp takes off, you could program the ignition system to retard.

Boll@@@s

Edited by shane on 9th May, 2018.

Ok all this is great feedback and since I am fairly proficient with electronics (I have built a 3D printer a drone and worked on many Raspberry Pi projects before) I am getting excited about building a smart turbo classic mini!!

I am thinking that I could set up an arduino to be the brains of my car controlling boost via pressure sensor and solenoid, managing water injection and functioning as a general warning system monitoring various aspects (temps/pressures) to keep me from damaging the engine..

I searched in the forums for arduino but it seems it hasn't been discussed before in a Turbo Mini forum. Searching on Youtube though there are a bunch of videos with DIY solutions.. I'll do some digging and revert, maybe even start a build thread as things get move from theory to action...

Any ideas/thoughts are welcome!

My car is a 1975 saloon and the engine is an A+ 1275 out of an Allegro. Distributor is a 123+ TUNE and I am currently going through the engine rebuild phase.

Nik

For the love of cars!!

check out Speeduino,

you can get the pcb for not much and get the parts kit from mouser or digikey, its kind of like Megasquirt was years ago before it got really complcated.

Great stuff Joe, looks very interesting!

However I do plan on keeping my car running on a carb rather than injection so I guess most of the speeduino functionality would be pointless....?

Having said that maybe I can learn from it (definitely on controlling boost since it is an included feature) and develop something for water injection.

I will be doing some extensive research in the coming days.............

For the love of cars!!

True, but in my opinion, on a turbo motor its WELL worth having an ecu to be able to log stuff, especially boost and AFR, and in your case if you really dont want to go the intercooler route ( I really really would fit an intercooler) then logging air temps will be really worthwhile during testting/ setup.

apart from all that you'll always get much better ignition contol with a proper 3d map

I'm with Joe, the Speeduino is well worth a look esp. if you are familiar with Arduino and its code generally. I'm playing with one at the moment as a side project.

Just using it for ignition has got to be cheaper (as you say you're into DIY type electronic projects) than any of the other 3D igntion systems and, as Joe says, you can modify it for all the extras you want (esp. datalogging)

And the interface is TunerStudio which as anyone who uses MegaSquirt will know, is a very nice interface. In fact I'm not really sure why Phil Tobin gave them official permission to use it, Speeduino is very much like how MegaSquirt started out and the guys really into it are already running it on the more powerful Teensy boards or even directly on an STM32F407VET6 or similar ARM chip.

So, just like MegaSquirt started off as very simple and DIY but nowadays has some quite powerful versions available, I wouldn't be surprised if Speeduino didn't follow a similar route.

Schrödinger's cat - so which one am I ???

Thank you guys, I am officially convinced and will incorporate the speeduino into the build! Will probably start a thread on its own when it is in the making.

What is the best solution for adding a crank sensor to a non MPi/SPi mini? Do people generally use a VR type sensor? I saw the kits for Megajolt, is that my best option?

For the love of cars!!

I strongly think you should also be “officially convinced” to fit an intercooler.

Let’s be blunt and honest with the future chain of events which will happen and are as certain as death and taxes.
You’ll run a low-ish level of boost and love how it drives, you’ll then want to increase the boost / power level which will nessistate running one. There’s no point denying it as it will happen it’s happened to us all!

So why not build it once and build it right, an intercooler can be installed to look factory fit with enough thought and time without a massive cost, I believe Sprocket’s 16v build has a factory aire to it.

Aesthetics aside, you should really fit one for efficancy and “safety” of the engine.

To quote Benross (IIRC) more boost isn’t the icing on the cake, it’s just more cake!

Shane.

Hi Shane, and thanks for the feedback. I'm sure you know what you're talking about and I value your opinion. Unfortunately the intercooler limitation is there because I will also use the car to participate in historic racing so something as eye-popping as intercooler will be hard to "support", whereas a setup similar to the Metro Turbo or ERA Mini with just a plenum will be more in line with the spirit of the historic racing club.

Been doing some extensive research over the past days on speeduino, I hope I had learned about it before buying a 123 TUNE+ programmable distributor as I understand that this will now become obsolete since timing will be controlled by the speeduino.

Being able to design a 3D map using intake air temp as an input is a great solution to my case since I will have water injection but it might not always work (intentionally or by fault) and having a smart ECU that will adapt the timing accordingly can save me a lot of trouble down the line. On top of that controlling boost will also be a key task of the ECU. If I set up both maps based on Intake Air Temp I think that if I have a switch on the dash to turn water injection on and off I will have a "two-speed" engine, one to give me a big smile on my face and another to give me a huge one

For now I need to figure the best and most discrete ways of setting up the sensors needed for the speeduino (cam, crank, MAP, and maybe even knock) which I hadn't planned for earlier and if I am going to be doing any drilling and/or taping on the block or other engine components it will need to happen pretty soon. Been doing some digging around the forums and there's a lot of info to digest but I think I'll figure it out eventually...

I think a separate build thread is warranted, for now I will take the engine to the machine shop and set it up for a 8.6-8.7 CR and do tons of research in the meantime!

Thanks for the continued help, I hope I will be able to contribute back to the community by sharing my build..

For the love of cars!!

It really depends on how discrete you need to be for the rules of your historic racing class (where are you based ?).

Any ECU that controls ignition timing needs a crank signal, usual way is a 36:1 missing tooth wheel on the crank fanbelt pulley with a VR sensor. A hall sensor would be a bit more modern but either way, even if you have the 36:1 teeth milled into the standard pulley itself, it's going to be quite obvious to anyone who knows what they are looking for.
Equally, if you use an ECU for ignition, you would normally change the single coil and distributor to a wasted spark coilpack (or even a full coilpack or COP or CNP) and these are all fairly obvious.
You could use the ECU to trigger a single coil and stick with the dizzy to put the sparks to the right plugs but, IMHO, you would be wasting your money on the ECU (whatever one you choose).

A bit more information on what rules you have to follow would be useful.

Schrödinger's cat - so which one am I ???

I can't say i have ever heard of racing regs that would allow you to turbo a non turbo car and fit a modern ignition setup but not fit an intercooler because its not period. not to be rude but it sounds a load of rubbish to me?

If you are using it on a circuit you really really want be using an intercooler. The whole reason your turbo'ing it is to go faster right?
Why chuck away what is essentially a free massive HP gain and an added safety feature.

A lot of cars on here (mine included) are using a ducted side mounted intercooler and putting the rad up front. It works and looks factory-ish.

Hi Jonny,
the racing I'm referring to is historic TSD racing and there are no "hard" regulations as to what you can do to the car, it's more about what I feel comfortable doing to my car in order for it to be considered a "relatively" period correct vehicle.

The truth is that the modern ignition setup is also something that is troubling me apart from the Intercooler as it will be quite an obvious change in the engine bay.

So let me rephrase and clarify, it is not so much a matter of what I am allowed to do with it, but rather what I want to do with it. Ideally I want an engine bay that will look as period correct as I can manage. A metro turbo setup is the goal here, but with the added feature of water/meth injection (which can be very discreet) and even better would be ignition control but I am not 100% sure about this yet. I do have a programmable distributor but it will not be able to pull in intake air temp and map ignition against it, which is a real bummer.

Back to the drawing board for now........

For the love of cars!!

We're running 10 psi on our 998T with no intercooler with no issues. We are going to fut one fir 12psi eventually but other than not getting possibly the full amount of available power by not having one, it's been okay. It does get a little warm on hot days but that's probably down to still using stock cooling still.

Thank you for your input carlzilla, it is encouraging to know that it has been done before with success!

I spent the largest part of last night studying David Vizard's Bible and in the section that talks about forced induction he talks about a setup with 8.5CR which could be boosted to 12-13 psi and with the addition of water injection could go up to 18psi (all of this without an intercooler). I think if I couple this with the feedback from this thread I can safely infer that it is likely possible to go the non-intercooler route and as far as CR I will aim for 8.5-8.6 since that is something I need to determine at this part of the build.

I will start a build thread since there is lots of stuff going on and a lot of questions that keep piling up so hopefully people can help me and the thread can also work as a reference in the future.

Cheers everyone!
Nik

For the love of cars!!