kevin
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Re: Jim K. 3.2 engine

Post by kevin »

Cutting aluminium plenums with grinder is scary stuff as they disc clog up to quickly and can shatter so you gotta be extra careful . Some plenums I cut the coil pack cover part off as it made it easier to weld the new triangular chamber on . If you leave bottom section on it then weld the bottom plate of the chamber first from the inside then you guaranteed of no leaks through pinholes .
Jim your addition of chamber depends on how much bend you want to put on the intake pipe to the throttle body . Atleast you got more space in the 75 .
I guess its difficult to tell when your neighbours are getting upset with you in Greece as you could mistake a plate landing on your work bench as a ricochet :D
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Re: Jim K. 3.2 engine

Post by 75evo »

WTF, 10:30 with a die grinder!? :lol:

Actually I'm thinking of getting a cheap China plasma cutter.
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Re: Jim K. 3.2 engine

Post by Jim K »

I admit I was a bit scared and took extra care to hold the composite cutting disc straight and the grinder with both hands. And to think I took the disc guard off for better visibility..... :shock: :wall: I would prefer if the thing had a foot switch for safety. Anyway -what a relief- its all cut now and I'm at the ...artistic stage of cardboard cutting/modelling! :roll: Good thing I had a proper protection suit on.... barefoot with a pair of shorts! :D -it was 35*C outside! I did however wear goggles as last year I had to spend hours in hospital, waiting for an eye-doctor to remove a tiny aluminum chip 'Gees the damn thing hurt like hell!!!
Kevin, I intend to have the bottom piece welded first at the right downward angle (over the coil packs). The top piece will also incorporate the side plates which will be bent downward 90*. The rest is easier, although Some difficulty I expect with the TB mount area. I will post pics today after I finalize the cardboard art!
There MD, I unfortunately managed to stay alive... again... :twisted: Your loss! :mrgreen:
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Re: Jim K. 3.2 engine

Post by Jim K »

After some cutting, here is the final shape of the box. No great accuracy is required as alloy weld seams are fairly wide and can cover minute imperfections. Thursday is water-jet day so I'm slowly inching along. The throttle body area will probably get a double plate.
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maxiboy
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Re: Jim K. 3.2 engine

Post by maxiboy »

Looking Good Jim .. not hanging around
Jim K
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Re: Jim K. 3.2 engine

Post by Jim K »

My first ever (and last?) fwd modified plenum is home. The water jet guys did a good job yesterday with 5mm thick aluminum plate and welding was done today. I actually like the way it looks. Its not finished, as I still have to attach the TB flange, idle motor mount/hole, brake booster hole, maybe 1 or 2 small vacuum ports and a couple of mounting lugs to fix on the valve cover. For now, I'll have to cut the TB hole and get all necessary bits ready for the next welding visit.
Another nice thing I did today is the oil-priming special tool which will only fit 164-based 24v engines. The one I had made for the 12v engine did not fit as the shaft fouled the head casting hopelessly. To get around it, I made a new tool with a 1/4" joint and extension as shown below. The engine pre-start priming problem has therefore been solved.
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gtv-racer
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Re: Jim K. 3.2 engine

Post by gtv-racer »

Looks nice Jim!

Just one question. Is the original throttle body big enough for all these nice mods?
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Re: Jim K. 3.2 engine

Post by Jim K »

According to several books and sites, its more than enough for street/trackday use. For a race engine, they say 74-76mm is best. See here: http://www.hipermath.com/engines/throttle_body_size
Some people in this site also have verified no change by going bigger, even with 3.7 engines, so that is a good excuse for me to retain std size -and cheap too! 8)
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Re: Jim K. 3.2 engine

Post by 75evo »

Ooh never knew that. So I can retain the stock 75 V6 TB? Nice! Cheap tips and tricks from the Greekster.

My 156 3.0 has 68mm though. Might have to go with a Porsche 996 TB for this one.
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Re: Jim K. 3.2 engine

Post by maxiboy »

yeah standard is the 67mm at the exit..

i think the larger commonly used items are used to hide a flaw in the inlet manifold being to small in capacity but they probably hurt throttle response.

As i,m going for a 3.7 and using the standard inlet manifold modified for larger capacity ( at least to start ) i,m going to use a 70mm unit..

I think 76mm or larger 84mm probably effect the engine rather than add gains..

Jim K any chance of some flow bench testing of throttle body manifold and head together.

If you get bored :D
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Re: Jim K. 3.2 engine

Post by Jim K »

Nice idea but not very practical to carry out, as it becomes very cumbersome and the flowbench space is barely big enough for one person/operator -much smaller than a phone booth! The plenum would have to extend so far out and leave no room for the operator, as the head under the plenum can't be used -no access to manipulate the valves.
I spent several hours yesterday trying to find the best arrangement for the throttle cable. Must be at the correct angle and position. Still have to do the two supports for the plenum on the valve cover. This is the kind of work I don't like, trivial time-wasting stuff! Will post pics when done.
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Re: Jim K. 3.2 engine

Post by kevin »

Jim you actually don't need any supports for the plennum as the six rubbers hold it in position really tightly ( if that's a word) and when you add the intake pipe it will be supported on a rubber bracket so it all works well a a unit .
I preferred bringing cable from underside using the 164 bracket but others made their own bracket and came over the top of the plennum . One thing we all did was we used a 50mm diameter wheel on side of Tb as this became the best ratio to the accelerator peddle travel .
Some pics of two types of cable set up .
You also have to bend the throttle cable bracket on the body to change its angle as the cable will run directly into the plenum .
Some pics of both cable set ups . Top is probably better as the cable does not get hot .
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Jim K
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Re: Jim K. 3.2 engine

Post by Jim K »

Nice pics Kevin! This is exactly what I've been doing for the last couple of days! I've been dealing with the cable issue and decided on the gtv6 metal bracket and cable routing, that is, the cable coming from between the chrome pipes under the plenum. Its a bit tight but I think looks neat.
I want to support the plenum with two nice brackets which will mount on the existing valve cover holes with rubber isolators and M6 bolts. I believe it will also look good and I will be able to post pics maybe tomorrow when I expect it will be all done before painting. I also squeezed the idle motor next to the TB. The 164 cable bracket seems huge and I opted not to use it, since the TB itself is from gtv6. I like the fact its smaller than the 24v on the outside but with same ID. I will have to make a simple small sheet aluminum adapter plate though for the TB potentiometer, as the two gtv6 mounting holes are farther apart (made for the larger TB switch).
I'm slowly getting there. When I'm done with this plenum, I will make an oversize gtv6 plenum (cutting/welding two std ones) with proper size pipes underneath. I intend to compare performance (dyno) with each type and see how close simulator results are to the real world. 8)
Jim K.
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Re: Jim K. 3.2 engine

Post by kevin »

Jim , have you pi#%d off your neighbours so much that they have put time constraints on your plenum progress :wall:
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Re: Jim K. 3.2 engine

Post by Jim K »

Hhahah! I pi$$ed them good allright, on and off for a week and then some, morning and evening. But in the end they found peace and I finished my stuff! Too bad the color (electrostatic paint) doesn't bring out detail but you can see the basics. Notice the metal plate holding the TPS. With the given TB, its the only angle possible for mounting it. These coming days you will also see the enlarged rwd plenum. I will have to visit my header shop, to have him make 6 proper runners using the mockup I made for the ITB's. All in all, its getting close to finishing time meaning: fill with oil and pressurize! Just give me a couple more weeks.
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