[trackday_prep] Cameron's Mi16 / Gti6 Hybrid

[Cameron 16]

Oh yeah I know what you mean, not even the best laid plan survives first contact with the enemy.

 

I'm doing all the CAD work because it's easier for me to do at the moment - as in I'd rather be sat indoors seeing how things fit than outside in the cold scraping my knuckles.

 

Basically, if I get everything planned out now I can see what materials I'll need before I start work. I may be pretty good at fabricating stuff, but I don't have any way near enough experience to go out, look at an engine bay and say confidently that I'll need some of this, some of that and one of those and it'll all come together perfectly. This way I can get all (well, most) of the trial and error out of the way on the 'pooter and all it has cost me is a few hours of my time, rather than any expensive materials.

 

This is a development really, so there's bound to be hiccups along the way and I'll definitely share them! This would be a very boring read if I just showed the design, then showed the finished item and said there you go, fits just how I wanted. That's clearly not going to happen, so I'll make sure I leave in any juicy bits!

[DrSarty 90 1 Cars]

Okey doke.

 

Just another note. My bodies as others I've seen are mounted with the fuel rail underneath. This can help clearance, locate the throttle cam to a simpler to plumb in side, and (rather randomly and according to Magic in Brisbane), produce better power, as he's proved in back to back tests. Pinch of salt on the latter point if you wish.

[Batfink 201]

Rich, its certainly possible in theory as the fuel will get better atomisation as it sprays up as its less likely to run down the inlet and can hit the top of the inlet and separate more. Where did magic get better power, low and midrange?

[Cameron 16]

Aha well that makes sense! I've decided to copy you and mount mine upside-down too.

 

I've been doing a bit more today, most of it being a massive ballache sifting through the garbage on the internet to try and find some decent information. I found a pretty decent looking method for calculating the inlet length, and it works out to 395mm for peak VE at 6500rpm, which seems reasonable. I'm having some trouble finding anything on calculating airbox volume though, but I've had a go at making an airbox that will fit and it's easy enough to modify should I find the volume has to change.

 

Some pretty pictures..

 

Trumpets inside the airbox - airbox hidden

 

Airbox shown

 

 

I think I'll try and make the airbox out of prepreg carbon fibre, as we have the facilities at uni.

The difficult part is trying to get a decent inlet to the airbox, and trying to incorporate a filter. I may well end up settling for a Pipercross ITB filter, which would be nice 'cos then I have something secure to bolt the airbox to. Will have to see how it goes.

[EdCherry 34 1 Cars]

Id be tempted to say why not go for a panel filter across the front. Although it might not be as effective as you would like, it might also be less damaging as the above design can often be a limitation and decrease power.

 

I dont have personal experience in this, but just airing my view's based on the information I have.

[Spiky 37]

be interesting to know the difference between that and my setup

 

 

off topic, have you spoken to ASH who has the same setup as you, mi16 gti6 , he changed back to full gti6 as he had major oil issues, maybe worthng speaking to him?

[Cameron 16]

Well I've read rumours on t'internet that filters in front of the trumpets can mess up the pulse tuning, I'll have to have a chat with the people at uni when I get a chance and see what I can do.

 

Nope, haven't spoken to him about it. What were his major issues? I haven't had anything yet.

 

It's a long way off being made at the moment, I want to make sure everything is right before I start making anything, but yeah it will be interesting to see if all this head scratching was worth anything.

Edited February 2, 2010 by Cameron

[Spiky 37]

at combe, when cornering, it just emptied all it's oil , we tried a few fixes on the day, but it was game over

 

while on the road, it was fine, just on track, it showed up a down side

 

yeah, be nice to see the difference, you then have to ask, is it worth it for a few bhp?

[swordfish210 20]

Ash's problem was that the engine would blow all it's oil in to the breather tank after about 5 laps on the track. Seeing 4 litres of oil being rapidly forced in to a 1 litre tank was strange to say the least. It worked fine on the road though so trying to solve the problem was becoming expensive for him.

Edited February 2, 2010 by swordfish210

[Cameron 16]

Aha ok I see.. Yeah I had issues with my breather set-up at first but eventually got them routed so they don't spew out any oil. It's done a few laps of der Noiboigring and not had any problems, will have to wait and see how it gets on with tighter UK tracks this year.

 

As for weather it's worth it, it is to me and I guess that's all that matters. Working everything out first is something I want to do so I can understand the problem completely. I could just go to a website like this one, plug in my numbers and get a value, but that wouldn't help me understand anything! Likewise I could make a mock-up manifold with adjustable runners and a few different airboxes and test them out on the dyno, but I can't afford the dyno time.

[welshpug 1,661]

like ed i have no direct experience of the air filter setups, though can't help draw comparison to the setups I have seen used by the Maxi kitcars, a fair sized panel filter right up behind the grille, quite some way in front of the mouth of the trumpets, maybe this wouldn't have such an effect on the pulse tuning you mention though they are generally in slightly longer engine bays, not dramatically though.

 

if its not too costly to make some temporary prototypes you could easily enough monitor how the engine responds to the two approaches from what intake temperature and exhaust mixture logs you'd get.

 

I.E get out on the road and play

Edited February 2, 2010 by welshpug

[EdCherry 34 1 Cars]

I can see why you have doubts on wether the panel filter is the way to go, but you got to weigh up the amount of money and time your going to put into it for the power your going to get. Not to be harsh but your airbox design could be s*it, then again so could the panel filter. The way I feel though is its easier to get the panel filter airbox design right over your design.

 

Of course the main aim is to get above atmospheric pressure in the airbox, maybe if you could fork out for a second box and a bit more dyno time you could trial both and sell the one you dont want to use. After all they might both affect the car at different points in the range.

[Cameron 16]

I think you're right, I was getting pulse tuning (runners) and Helmholtz tuning (plenums) confused. You get problems when you put a filter in a plenum designed as a resonator as the foam absorbs the air vibrations. The pulse tuning will be fine as it is only concerned with the area immediately in front of the bellmouth. I think.

 

From what I've read on t'internet Helmholtz tuning (using a plenum) is only useful at low engine speeds, and becomes ineffective at high rpm. But that's totally contradictory to what I've heard previously, and I know a lot of thought goes into plenum volumes for out FS car, which uses a bike engine operating at high rpm. I'll have to have a chat with the guys sorting the engine and see what actually makes a difference.

[Liquid_106 97 1 Cars]

I'm having some trouble finding anything on calculating airbox volume though, but I've had a go at making an airbox that will fit and it's easy enough to modify should I find the volume has to change.

 

I know you've not finalised the design of the airbox from a dimension/volume aspect, but from the ones I have seen, they tend to narrow more towards the TB furthest away from the box inlet:

 

 

I can only assume it has something to do with maintaining an even air pressure across all four (or six in the example above) inlets, so not to lean out one cylinder in comparison to the others?

 

Of course I could be talking out my arse, but it may be something to look into / consider?

 

Love the build btw, but confuses me with yet another engine option to throw into the mix when I finally pull my finger out!

Edited February 10, 2010 by Liquid_106

[Batfink 201]

correct. I once had a nice document about testing on a toyota racecar for that type of design, made a good read.

All the touring cars feed from directly in front though so I'd imagine that removes the issue. They just get a big enough airbox to stop the box affecting the throttlebody pulse tuning then duct from a high pressure area in front.

[Cameron 16]

Yeah I read that they taper so that the furthest cylinder doesn't get starved. I'd definitely prefer to have the feed come from the centre but there just isn't room for it. You'd need a good long taper out from the central feed otherwise it's going to bias flow to the centre cylinders.

[DRTDVL 4 1 Cars]

What about a twin intake setup a left and right side feed?

 

I know a few people that have modified their factory manifold to run a twin throttle body design.

 

Edited February 11, 2010 by DRTDVL

[Cameron 16]

Surely that does more harm than good? In that setup you've got two flow patterns coming in and colliding in the centre which must cause some pretty severe turbulence, and an area of higher pressure in the centre.

[Spiky 37]

i'm with cameron here, surely that would only be benificial if there was an ait gap between the middle two?

 

would be very interested to see a before and after comparison of a single and double setup

 

cameron, on your setup, i would also suggest getting EGT sensor in eash ex pot to see if the egt's are the same accross each cylinder

[Cameron 16]

That would be very nice! But I'd also need some data loging equipment as the Emerald is pretty useless, and that stuff is expensive!

[EdCherry 34 1 Cars]

Just to throw this in the mix

 

 

What you think looks wrong, isn't always. Intake is so small because that is the restrictor.

 

This is a pretty good (my understanding of this design anyway) airbox for an older F3 car providing a nice even spread across all 4 cylinders...

[Cameron 16]

But that's making the best of a bad situation (or set of rules), rather than being an optimum design. I bet if they had free reign to design whatever they wanted the airbox would look much different!

[Batfink 201]

My plan is to move to a smaller radiator so I have more room out the front. I will work out with Kyepan the best high pressure zone on the front of the car and shape the induction to duct from there as he has a nice little gismo for that i'm itching to play with...

[Cameron 16]

That's a good idea, what size radiator do you reckon you could get away with? I've got a standard BX one at the mo and it has no problem with cooling, even at full death round the Nordschleife in summer. I reckon I could get away with a much smaller one, especially if it's alloy.

[Batfink 201]

theres probably some sums to work out there but I will try to go at least half the standard size, probably a thicker core and run proper ducting to channel through air in and out to make the radiator more efficient. I'll have the car back from colin in a few weeks so will start measuring up then to see what is truly feasible.

I think there will be an element of trial and error to get the engine performing at the right temp but it will be a good experiment