Trav’s Race Build: from B6 to Big Bore BP-Z3

[Scoota]

Oh boy…




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[StanTheMan]

Tell us the profile

[Scoota]

Yes, my camshafts have arrived. I can hardly believe it. These are from Cat Cams, part # 3702606:

http://www.catcams.com/products/camshafts/datasheet.aspx?ENGINE_id=351&CAMSETUP_id=2335

Cat Cams 3702606.JPG

There aren't many cam options that retain the VVT actuator. Maruha had a couple of options, and they even offered me a custom grind, but I settled on these bad boys. I've always maintained that I don't want my usable power to be right up in the top end, so these aren't what I'd call "wild cams", but let's hope they get my head breathing a bit better. My head has already been ported, and it has +1mm larger SuperTech inlet and exhaust valves. I've already fitted Cat Cams valve springs PAC-S90015 with Cat Cams CC017 shim-under-bucket cam followers, plus shims to suit.

Intake Valves: https://www.supertechperformance.com.au/p9096-maivn-1206-hi-flo-black-nitrided-intake-valve
Exhaust Valves: https://www.supertechperformance.com.au/p7742-maevn-1206-black-nitrided-exhaust-valve
Valve Springs: http://www.catcams.com/products/valvesprings/details.aspx?VIEW_PRODUCT_id=10
Cam Followers: http://www.catcams.com/products/camfollowers/details.aspx?VIEW_PRODUCT_id=835

I wonder if it will work...?
Anyone else out there using the Cat Cams 3702606? I'd really love to hear your experience.

[StanTheMan]

I had virually the same profile in a 1.6 and loved it. My current cams have way more lift and slightly different LSA. mine are 108 so lift together with the LSA would give me slightly more torque perhaps . In my 1.6 I had standard compresion. In the current 1,8 Ive got a tad more than 11:1

with the VVT you should be able to get the idle very nice. & recite poetry at 7000 rpm.I had an old adaptronic with mine. in the 1,6 and it was a total bitch to drive low down. I found it better with the OEM ECU. no it wasnt as intense probably lost 10 RWKW.. byt it was such a joy to drive.

I have none of those issues with the MS2 now.

[StanTheMan]

just had a look at the Tighe 935C profile. perhaps slightly less aggressive than yours .
Anyway you'd be able to daily & sill have a shitloads of fun with it

[Scoota]

Hey StanTheMan, thanks for the comments. You're right... Idle tuning should be a breeze with VVT, and I'm also going to install an Idle Control Valve (ICV) to give me even more control, so it should be relatively easy. It won't have a lumpy idle like some mad-hat Miatas out there, but I'm okay with that. Mid-range punch and reliability is what it's all about for this engine.

Just thinking.... I could probably tune the VVT to give me loads of overlap and lumpy idle for extra pit-lane points and head-turning potential, if I really wanted to, but I probably won't.

[Scoota]

I've been chipping away at the hot-side coolant reroute. This is my design for the bracket that will support the M-TUNED thermostat housing. I think I'll be using 5mm aluminium plate for this one.

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[StanTheMan]

Just thinking.... I could probably tune the VVT to give me loads of overlap and lumpy idle for extra pit-lane points and head-turning potential, if I really wanted to, but I probably won't.

I did that with mine. LOL I love it. (the hard Parker within me LOL)should rock up to one of the Roadster Bro's meets ..... should get plenty of Kudos at entry. I have yet to make up my mind if they are Hard Parkers or not. All their cars are soooo immaculate. Its time to make one of those meets & get the real lowdown them

[Scoota]

I did that with mine. LOL I love it.

Legendary!! Nice one.
I'll definitely have to try it. If I can get lumpy idle and good throttle tip-in I might just leave it that way.

[Scoota]

I started with some head scratching and brain storming about an ITB airbox recently. This is a bit of a side quest, but definitely an important development in my mind. I currently see inlet air temperatures north of 60 degrees C at idle, and around 40 degrees C out on the track. Waaaaaaaaaay too hot! An airbox is definitely required, but I haven't figured out how to do it yet, because I want to increase my trumpet length to around 130mm (trials required to determine optimum length). I have 72mm trumpets at the moment. I bought a 52mm elbow that matches the throttle inlet and my trumpets, and I'm messing around with cardboard to see how they might be made to fit. The silver trumpet is off my current setup, and the red trumpets are on their way to me from eBay.

My plan is to make a fully enclosed airbox with curved trumpets inside it. Early indications are that the front trumpet will poke through the bonnet, even with it laid over. I don't think I want that, so more head scratching is required.

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ITB Manifold Pic 3.jpg

[RS2000]

I read somewhere that, for velocity stacks to work, they had to be tapered for the full length?

[Scoota]

Hey RS2000, I’m no expert but I don’t believe that’s the case. A good shaped bell mouth is important, but the taper is not. A nice tapered bell mouth is probably a good thing, but the opening is the most important factor. Once the air is into the trumpet (a.k.a. velocity stack) via a nice smooth bell mouth, the taper probably has very little impact on the “performance” of the trumpet.

After the bell mouth the next important factor is trumpet length. I’ve scratched around for informative advice on tuning the length of the trumpets and this is the best article I’ve found…

https://www.emeraldm3d.com/articles/emr-adj-length-intake/

In a nutshell, the trumpet length determines the harmonic frequencies (pulses) in your trumpets which can increase or decrease the velocity of the air being fed into the cylinders at certain points of the rpm curve. Different length trumpets will move the torque around, as per the article. Some trumpet lengths smooth out the torque curve and others cause dips and lumps. I’m paraphrasing and over simplifying, so please read the article for a more detailed explanation.

If you want to get really scientific you can calculate the harmonic frequencies, but I haven’t bothered. Sorry, I don’t have a link to the algorithms, but there is some good chat about it in the ITB section of this forum.

I’ll hopefully be doing similar to what the author of the article did and testing some different lengths on the Dyno, but not for a good long while. As I mentioned, the ITB airbox and trumpet fiddling is a bit of a side quest. I’ve got camshafts and the coolant reroute on the critical path at the moment.

I’ve also been considering a switch to E85. Now might be the right time. It’s almost free horsepower, right??


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[Scoota]

Also… Straight trumpets with a small bell mouth are apparently good enough for BMW’s M5, so they’re probably good enough for me…




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[greenMachine]

I read somewhere that, for velocity stacks to work, they had to be tapered for the full length?

Short answer - yes and no.

Length is important (are you looking for top end or mid-range power?), as is an efficient bellmouth.

Taper results in acceleration of the air as it is 'squeezed' down the tube, the better for cylinder filling amongst other things. So the straight trumpets will 'work', just tapered ones will (should) work better.

BMW may have gone with straight for pragmatic/space reasons, who knows?!

[Scoota]

The head finally got removed this week, and is off with my engine guy Ange Molinari of Molinari Race Engines. He’s going to install the new Cat Cams, measure up the valve clearances and order shims to suit.

Standard cams…






Look at those fancy pistons!! I wonder if my “big” cams will cause my valves to punch nasty little holes on them. Ange and I will work that out. We’ll be following Greg Peters’ examples on the Car Passion Channel, taking lots of measurements…

https://youtu.be/wegquiDjGlk

I’ll let you know how it goes.


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