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Author Topic: Ace GT Head Project  (Read 81624 times)

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Uncle Billy

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Reply #15 on: September 30, 2014, 08:17:25 am
Is it reasonable to assume that you'll produce more aggressive cams to take further advantage of higher flow rates in the ports?  And sell it all as a kit?
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ace.cafe

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Reply #16 on: September 30, 2014, 08:34:26 am
Is it reasonable to assume that you'll produce more aggressive cams to take further advantage of higher flow rates in the ports?  And sell it all as a kit?
It is possible, but we don't envision that as necessary in the street package which we see as a 6500 rpm range target.
The head will be equipped with high-ratio roller rockers which will give about .500" max lift at the valve, using the stock cams with .300" lobes. This puts the lift at the max that the valve springs can take before coil bind, and is as much or more lift than you will likely get from any cams in this engine. Our proven Ace beehive valve spring kit will handle all this lift and acceleration with no problems. We expect the package to be sufficient for 6200-6500rpm with the stock cams and our head.

This boils down to the idea that you won't need new cams with this head. The rockers do the job instead. That means you get the results at lower overall cost this way. However, if you already have other cams, or want to buy other cams for some reason, we can likely supply lower ratio rockers to accommodate that without exceeding the max lift height of the springs. I would recommend discussing those specifics with me beforehand. It is expected that NField Gear will release some cams, and once I find out those specs, I will work on configuring a rocker ratio to work with those, for anyone who wishes to pair these things up.

The throttle body size is going to be the limiting factor for max hp rpm, and we will try to make the most of what it allows. It should be good for the rev range we target.

Something like the Power Commander will be needed. Or a carb conversion kit. The rev limiter will need to be programmed to a higher limit than stock, and there will be some mixture map programming needed, and possibly some ignition adjustments. We can be more detailed about this part of it after we get into testing when it's done.
« Last Edit: September 30, 2014, 09:17:43 am by ace.cafe »


Uncle Billy

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Reply #17 on: September 30, 2014, 03:39:23 pm
Thanks for the response!  With breathing made more optimal it might be best to contemplate a conversion to a carburetor since adjusting mixtures is thereby not so dependent on arcane digital mysteries unsolvable in my garage (and probably 99.9% of everyone else's).  This then requires a change in the ignition system (probably replacing the original with one from Royal Enfield's pre-EFI past if it would fit), and pretty soon we're where we ought to be with a retro motorcycle - long stroke, deep breathing, manually adjustable, rev limited hot rod.  Sign me up!
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ace.cafe

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Reply #18 on: September 30, 2014, 03:46:34 pm
Thanks for the response!  With breathing made more optimal it might be best to contemplate a conversion to a carburetor since adjusting mixtures is thereby not so dependent on arcane digital mysteries unsolvable in my garage (and probably 99.9% of everyone else's).  This then requires a change in the ignition system (probably replacing the original with one from Royal Enfield's pre-EFI past if it would fit), and pretty soon we're where we ought to be with a retro motorcycle - long stroke, deep breathing, manually adjustable, rev limited hot rod.  Sign me up!

Carb conversion would be fine.
We plan a 34mm port on the intake. 34mm carb would be good, such as a TM34 Mikuni flat slide. We can bore our 32mm alloy manifold to 34mm to match, and it fits the existing UCE stud spacing, so it will bolt right on.
Hitchcock has an ignition conversion kit available with their carb conversion kit, and it may be available separately too. I believe it is derived from the AVL Bullet ignition system. Perhaps it even IS the AVL ignition package, maybe.
« Last Edit: September 30, 2014, 03:49:43 pm by ace.cafe »


p144

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Reply #19 on: September 30, 2014, 06:38:31 pm
Which setup has potential for more HP? Also any difference in throttle response (assuming proper tuning of each)?


ace.cafe

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Reply #20 on: September 30, 2014, 06:57:21 pm
Which setup has potential for more HP? Also any difference in throttle response (assuming proper tuning of each)?
I personally think that the hp potential of EFI or carb would be the same, given good tuning of each. Throttle response too.
The Mikuni TM series flat slide carbs are motocross racing carbs that we re-jet for our purposes. They have extraordinarily good response and power. We have been using them on all our Fireball and racing builds for years. Great carbs.

Basically, the port diameter will set the rpm limit at which the flow will be restricted with a given displacement. So, whichever the fuel delivery system might be, it is the port diameter that will govern the max rpm. And the max rpm will govern the max hp output.
So, with either system using a 34mm inlet diameter and the same port and valve, they will perform about the same as each other. Should be roughly in the 6200-6500rpm neighborhood for max hp rpm. Estimated power could be about 40hp or more, at the crank. Should do The Ton. That's basically what I'm aiming at for the output.

I'm trying to keep the whole thing as a head swap installation, so it's easy for people. And a new set of pushrods too.
I can control almost everything that needs changing, in terms of the performance parameters, with the design of the head. Get some mixture and ignition control for it, and it's in the bag. Pretty much can't get any easier than that, for a performance build.
« Last Edit: September 30, 2014, 07:11:58 pm by ace.cafe »


p144

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Reply #21 on: September 30, 2014, 07:58:34 pm
Sounds good to me!


Uncle Billy

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Reply #22 on: October 01, 2014, 10:34:46 am
How close to piston-valve interference does the increase in valve lift beget?  Since the camshafts are gear-driven there's little possibility that the cam drive will fail as a chain or belt drive system could, but is there a possibility that interference could occur by over revving the motor into valve float?
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ace.cafe

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Reply #23 on: October 01, 2014, 11:10:01 am
How close to piston-valve interference does the increase in valve lift beget?  Since the camshafts are gear-driven there's little possibility that the cam drive will fail as a chain or belt drive system could, but is there a possibility that interference could occur by over revving the motor into valve float?

We are going to set the piston-to-valve clearance distance when we design the chamber. We know the cam lift, and we know what rocker ratio we want to use, and we will be setting a valve angle and a chamber shape. So, once we have these parameters all decided, we can set a chamber depth which allows the necessary valve-to-piston clearance around the TDC area, so that the standard pistons may be used without clash. This is part of the design plan.

You see, since we are in full control of nearly all the parameters in this head, we do not have to perform gymnastics to fit things into some already existing design and casting that is basically set in stone. We can make it any way we want. And we will.

Regarding valve float, while this is always possible with a serious over-rev, our Ace valve spring package is high performance with advanced beehive springs and lightweight hardware that has excellent control over the valve and the spring harmonics and damping. It is the same basic package that has been successfully proven for years in our other Fireball engines, and has been reliable at over 6500rpm in those engines, and has shown perfect reliability and longevity for over 50k miles so far in those engines. So, we have a very good handle on the control of the valves, and it is not a worrisome problem in my mind. Never broke or lost any valve spring, or dropped or bent any valves, in any Fireball yet.

A few things we have planned for the package, and will be discussed for implementation in the design are:

New valve angle: The standard UCE valve angle is 26 degrees for each valve, 52 degrees included angle. This is relatively old architecture, and the more modern and efficient designs will use lower angles(such as 23, or 18, or 15 degrees, etc). This allows a more compact and efficient chamber for better combustion efficiency, allowing higher compression ratio, less ignition advance, faster burn, etc. However, it also can limit valve size a bit more, so a decision between valve size and valve angle need to be weighed, as well as how the port flow will work with the new valve angle. These all mesh in together, and we don't have a final decision on these details as of yet.

Valve size: We plan a bigger intake valve, and possibly a smaller exhaust valve to make room for it. This entails moving the intake valve guide and port inboard a little bit, which is no problem since we are designing the whole thing from scratch anyway.

Combustion Chamber size and shape: We plan a modern efficient compact(around 50cc) combustion chamber which optimizes flow and also allows higher compression ratio and more efficient burn for more power overall. Looking at somewhere between 9.5:1 and 10:1, depending on piston type and displacement. This will be a single spark plug chamber design.

Intake port: We cannot move the intake entry location from where it is, because we need the standard intake system to be able to bolt up, so that will remain where it is. However, we will port the head with the right shape to work with the new valve angle and the existing entry location, and the largest cross sectional area that is efficient with the existing intake system. Aiming at around 200+ cfm peak flow, with a nice fat low lift flow profile too.

Exhaust port: We are going to work with the smaller exhaust valve and a high efficiency exhaust port to utilize the exit speeds for best scavenging using a smaller valve and port, to allow us to use a larger intake valve and port. This maximizes torque, especially in the critical midrange rpms. Will bolt up with the standard exhaust header, the normal way.

Rockers: We will machine a mounting system for an entirely different rocker design on this head than the stock type. The stock rockers will not be used. The design will include a high ratio full-roller type rocker system, which will provide the maximum valve lift that we can fit with the valve springs that we use in our Ace Fireball packages(about .500" lift max). Ratio rockers also have the effect of extending the effective valve duration for increased rpm range, even though the actual numeric "seat to seat" duration is not actually increased., but everything between is lifted higher for longer. So, we get more duration and a LOT more lift with the same stock cams, which gives the performance increase we want, but saves money on not having to buy cams.

I realize that all these features will sound like a lot of money, but we have taken this into account, and we will be using available parts that do not need to be custom made, and are reasonably priced, so we can put the money in the machining of the head, and the parts and hardware are greatly reduced in cost compared to the custom parts we had to have made before, and all the hand porting and welding up chambers and lots of time on the various machines. So, this "should" come out in a very reasonable price range, not too different than what the hand-done head mods cost before, and give a lot more features and benefits in the package. It makes sense.
« Last Edit: October 01, 2014, 11:14:56 am by ace.cafe »


Bullet Whisperer

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Reply #24 on: October 01, 2014, 05:07:37 pm
Hi Ace,
 I assume a lot of thought has gone into this one already, but, would there be any advantage in using two inlet valves and one exhaust valve for this head? The reason I ask is one of several, in fact - two inlet valves can obviously be smaller and lighter, but the inlet valve is also the most likely to get too close to the piston when higher lifts and / or longer durations are applied - two valves of a smaller size would not only give better piston crown clearance, but they might not have to be opened so far, either. A central spark plug could be fitted right in the centre of the combustion chamber, between both these valves and a single exhaust valve which could possibly be larger than standard and / or have greater lift imparted on it. I realize two, three or even four valves might be possible, but the 87mm bore size might work well with three valves?
 Just a thought!
 B.W.
« Last Edit: October 01, 2014, 05:10:41 pm by Bullet Whisperer »


ace.cafe

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Reply #25 on: October 01, 2014, 05:34:46 pm
Hi Ace,
 I assume a lot of thought has gone into this one already, but, would there be any advantage in using two inlet valves and one exhaust valve for this head? The reason I ask is one of several, in fact - two inlet valves can obviously be smaller and lighter, but the inlet valve is also the most likely to get too close to the piston when higher lifts and / or longer durations are applied - two valves of a smaller size would not only give better piston crown clearance, but they might not have to be opened so far, either. A central spark plug could be fitted right in the centre of the combustion chamber, between both these valves and a single exhaust valve which could possibly be larger than standard and / or have greater lift imparted on it. I realize two, three or even four valves might be possible, but the 87mm bore size might work well with three valves?
 Just a thought!
 B.W.
Hi B.W.,
Yes, I have given that 3 valve arrangement a great deal of thought, and also the 4 valve. I really wanted to do something like that.
However, the cost issues involved were a lot higher, and the target power level could be served well enough by a good 2 valve layout. So, while I was(and am) quite attracted to the multi-valve layouts, I had to come back to reality with a price point that would attract enough buyers.

I had to make the call about feature/benefit/price analysis, and the 2 valve comes out ahead in that fight, based on a 6500 rpm limit from the 34mm inlet tract. We can flow all that 34mm tract's capacity thru a good 2 valve layout. Most buyers will want to stick with the maximum available RE throttle body which is already present on the GT, due to the cost of buying a different EFI system, so 34mm is basically it. Our valve spring package can easily control these valves at 6500 rpm, so there is no need for the lighter valves of the 3 or 4 valve system unless we move into a significantly higher rpm range along with a bigger throttle body EFI system, which I don't see happening on a street bike in an affordable range. Perhaps a carb conversion would be better for that kind of application.

However, I am fully open to anyone who wants to have us develop a 4 valve head, and is willing to purchase one, and pitch in a significant deposit to get the ball rolling. It is certainly within our capability, and Mondello's is already currently producing 4-valve billet heads for American V8 engines. So, it is very do-able. But we need customers who would pay that much for a more exotic cylinder head. In a "cost no object" market, this head would have 4 valves in it.

This advanced 2 valve head gives a lot of bang for the buck, and should be in an affordable enough price range to attract buyers.
That's the reality of it.
 :)
« Last Edit: October 01, 2014, 05:51:56 pm by ace.cafe »


Uncle Billy

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Reply #26 on: October 01, 2014, 06:51:39 pm
I agree that 2 valves is the best route, all considered.  Exacting the maximum power isn't of primary concern to me (YMMV), but a more hearty midrange that yanks on the bars when asked for, is.  Others may want to hop this thing up to its absolute max and that's fine.  But the balance you've taken between cost, feasibility, outcome and cost (sic) is right on for me.  40 hp at the motor would be just right, and a 6500 rpm red line is okay with me - long stroke motors with high redlines just wears out pistons and rings too fast IMO.
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High On Octane

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Reply #27 on: October 01, 2014, 08:54:10 pm
Keep in mind Ace, even if you design the initial head with a 2 valve set up, you will still have a CAD designed saved for the CNC machine work.  It would be relatively easy to go back down the road, take the existing head design and modify it to a 3 or 4 valve design.  And if the application seems to suit, it would be just as easy to modify and open up the intake and exhaust ports for a full custom race application where a custom aftermarket EFI system and custom fabbed exhaust could be installed on the build.  The joy of CAD design is that once you have your initial head designed and produced, using your imagination to push the limits of something more radical becomes more affordable, as the basic layout is already there and not nearly as much time is required to modify things in the CAD program like valve placement and intake/exhaust ports. 

I've been excited about this since I first heard about it.  I'll be following this with great interest.  8)
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mattsz

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Reply #28 on: October 02, 2014, 05:29:53 am
This advanced 2 valve head gives a lot of bang for the buck, and should be in an affordable enough price range to attract buyers.
That's the reality of it.
 :)

Sounds sweet!  You've obviously given some thought to the costs involved... when will you be able to give us an idea of how much all this goodness will set us back?


ace.cafe

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Reply #29 on: October 02, 2014, 05:53:47 am
Sounds sweet!  You've obviously given some thought to the costs involved... when will you be able to give us an idea of how much all this goodness will set us back?
I'm going by estimates right now. The development of the billet is on a "time and materials" basis from my guys at Mondello's, and that is just the way this kind of thing is. They have told me about what they expect it should be, based on their experience. It will all become more clear as we progress.

The aim is for it to be similarly priced as our other Fireball type head work. They say that they think they can do that. In fact, they suggested it to me as something they thought they could do in the similar price range.
When we get the figures more firmed-up, people can contact me about it, because I have a general policy to not directly discuss our pricing here on the forum.
« Last Edit: October 02, 2014, 05:58:11 am by ace.cafe »