39 replies to this topic

[MAGA7INE]

sounds like your mag is the kinda mag I like then! :wink:

all techy, with proper tech advice! (not bloody telling you to sink your valves into the head - like a certain someone did, in a certain mag)


as a sort of related Q, what sort of power would you expect a LONG stroke engine to make, before it starts ripping the conrods apart?

for example, a 1098, with a 12g940 head. Would you expect it to cope with 100+Bhp's worth of boost?





more curious as to anything else really

Thanks! The simple answer to your question is that I don't know as I have not done it and I wouldn't want to just make up some random answer.

I do know that my friend Jai of Minicranks in New Zealand turns these engines nat asp to 7k rpm with no problems. After that, they start eating bearings.

With such a long stroke, I doubt you would actually get the engine to the sort of HP/rpm levels where what I am talking about comes into effect. Again, it's not boost pressure that is the problem, it's rpm. The 1098 is almost self limiting in that respect.

Don't think I am saying anything other than a short stroke engine is rubbish, I'm not, there are lots of 13 second 1293's, I'm just stating the theoritical advantages of them, which I am testing myself with this engine build which I hope will go beyond the power produced before by some considerable margin

I should stress again, it's not boost that kills engines. Forced induction, (and I include nitrous oxide injection in this definition as well, it is just a chemical supercharger), also helps to reduce the tensile loads the engine sees at BDC as the vastly increased volumes of exhaust gas cusions the piston as it goes over BDC, with some extremely trick electronics I hope to be able to quantify this effect.

Sorry I can't answer your question further but at least that's an honest answer! Why not try one?!

[ditz]

Right MAGA7INE...
after reading all that you have just posted.. i WILL sucscribe to the mag when its out.
im guessing you will keep progress posted on here? il keep checking back.
fill it full of tecchie stuff! :grin:

[chairchild]

my god.............

you have just proven what an awesome mag it will be!!

You didnt make up a random guess - you simply quoted some limits, and the basic theory behind it! Better than a certian someone, may I add :wink:

hehe, and yups - might turbo mine next year, after I've had my fun of a silly MPG 1098



and yeeh, I understand how boost doesnt kill it, but I was wondering about the rate of expansion?pressures involved, wether the conrods would cope - especially with the stupidly increased rate of acceleration they might encounter :saywhat:

by the way: What sort of electronics would you be on about? Ignition?

[MAGA7INE]

my god.............

you have just proven what an awesome mag it will be!!

You didnt make up a random guess - you simply quoted some limits, and the basic theory behind it! Better than a certian someone, may I add :wink:

hehe, and yups - might turbo mine next year, after I've had my fun of a silly MPG 1098



and yeeh, I understand how boost doesnt kill it, but I was wondering about the rate of expansion?pressures involved, wether the conrods would cope - especially with the stupidly increased rate of acceleration they might encounter  :saywhat:

by the way: What sort of electronics would you be on about? Ignition?

Thanks! Honesty in journalism is a rare thing I know .

I should say I am at the very bottom of our tech writer pile, there are much more experienced and knowledgeable people who are also writing the tech columns for the magazine. My lips are sealed for now but trust me, you will like what they have to say

I am hoping to use a custom add on ECU (seperate from the engine ecu to start with, don't want any unfortunate accidents!), that uses ion trace sensing, this uses the feedback from the spark plugs in a special wasted spark mode to measure the actual real time cylinder pressure which can be calculated using the measured electrical resistance and some other properties, adapted from megasquirt hardware.

Based on the cutting edge ion sensing research I read in a paper in the SAE journal, pioneered by a PhD student. I have had a chat with the person who wrote it, (it turned out we had a collegue in common, small world!!!), and I am going to use my humble little A series in some MAGA7INE funded research to see if I can get this to work, which is not that likely, but, unless you try you never learn!

The upshot of this is in the end, IF it works, I can throw away the wastegate, use an elecric servo and base the air flow demands and boost levels on the peak sustainable cylinder pressure rather than manifold pressure, which is a really dumb way of doing it.

In reality I have about as much chance of this working as developing warp engines in my workshop, still, keeps me amused

MAGA7INE is also arranging to fund the development of port injecting the 5 port heads with the freely available megasquirt boards and open source code, (so it will be free for all to use for the benefit of the Mini community, not for us to make money - putting something back!), by supporting the clever people doing the work, so we will have lots to write about.

We will let you all know as soon as we are ready to go, won't be long

[chairchild]

so in essence, you'll be making a super-complicated boost controller, which makes sure the engine will only get a certain amount of boost for the engine's rpm?

Certainately sounds like an awesome idea, since it should let the head gasket and piston rings live a little longer, whilst not having to use the (rather inneficcient) wastegate design


only problem I can see, is if you wanted to have a little "lead foot" moment, you'd be fighting against the servo, and you might end up slowing down! (which would be rather annoying)

In reality I have about as much chance of this working as developing warp engines in my workshop, still, keeps me amused

hehe, dont worry - I've designed a secondary engine that uses the waste heat of the exhaust to create a power source, with a theoretical output of 160% of the original engine :saywhat:

CBA to really go into it - but it's one of those "pipe-dream" projects

hehe, oh for the want of a workshop and TIG welder!

[lowridermini]

Iwould like a mini metro turbo engine but they are hard to get hold with and a lot of money

[Wil_h]

If you want a turbo charged mini you don't need to start with a Metro Turbo engine. They're nothing special.

[lowridermini]

but they are vary vary fast my mates one hade a subru imbrezza down the motor way he dont have the car anymore

[Turbo Phil]

What Will means is that you can use a normally aspirated motor as your basis and Turbocharge that. You don't need to have a Metro Turbo engine.

Phil.

[AlexF2003]

but they are vary vary fast my mates one hade a subru imbrezza down the motor way he dont have the car anymore

Reeeaaaaaaaalllllllllllllyyyyyyyyyyyyyyy

Did it have him on the "twisties" too??

Alex

[Jackman]

but they are vary vary fast my mates one hade a subru imbrezza down the motor way he dont have the car anymore

Reeeaaaaaaaalllllllllllllyyyyyyyyyyyyyyy

Did it have him on the "twisties" too??

Alex

I bet the guy in subru was not even trying lol.

[Sam]

but they are vary vary fast my mates one hade a subru imbrezza down the motor way he dont have the car anymore

Pure comedy! Even a spastic couldn't spell that badly!

Amazing story.. I can beat an Impreza 1.6 GL too..

[The Matt]

but they are vary vary fast my mates one hade a subru imbrezza down the motor way he dont have the car anymore

....Even a spastic couldn't spell that badly!........

That aint very nice! >

Back to topic!

So, to summise a little. A short stroke high revving turbo is a possibility.

With a 73.5mm bore and some 18cc pistons, you could run a high revving 1340 (or destroke even further). What sort of turbo would be used for a build like this, and would CR need to be dropped further as the engine would be revving higher than yer average T3 boosted MG lump???

Would something like a lower inertia T2 turbo be better for a higher revving engine? Maybe run a small level of boost, but over alot wider rev band (like 2.5K rpm through to 8K rpm)???

[minimole]

i may be wrong, but my understanding is that with a short stroke engine n/a or forced induction, the whole point of them is that they can rev more. so i would dare to say that they might be lacking in lower end grunt and most of the power is produced at the higher ends of the revs.

i also think it would be safe to assume that if an engine is reving higher it will be producing more exhaust gases thus being able to spin up a larger turbo. in which case my guess would be that a t3 turbo would be better for a short stroke. although by the same hand i guess if you want power lower down you could use a smaller turbo so it would spin up quicker and help compensate for the lower end torque.

I suppose if you wanted to use it on the road where you are not always at high rpm then the t2 may be better suited but if you where using for tracks where you are more likely to be at higher rpm and therefore on boost more often the the t3 in my opinion would be better suited.

however and this is a big however since i have no experiance with forced induction i could (probally ) be talking C**p and if i am please someone tell me and correct me, otherwise i will never learn

[The Matt]

......although by the same hand i guess if you want power lower down you could use a smaller turbo so it would spin up quicker and help compensate for the lower end torque......

That was why I was thinking it would be beneficial to run a smaller turbo, to give a higher revving engine more torque lower down the revs.........? I am also a noob in turbo terms and was just asking the question really. I was thinking that one day (in my dreams) I would like to build a really high spec motor and maybe that a shorter-stroked engine with a high rev band would be great for gearing etc, but the turbo could help give it some real low down grunt. I am just not sure what would happen at higher RPM with a turbocharged engine. I know some high revving bike engines have turbos fitted to them ('Busas being one example).