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Truth or heresay? OS Giken to finally reproduce the TC24-B1 head


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5 from crank to cam on an antique design. I am describing the number of interfaces that have clearances that add to inaccuracies and can also cause harmonics.

 

What engine are you talking about now? Both the Peugeot V8 and Ford DFV are V engines, and you appear to be counting only one bank.

 

If the gear-to-gear tolerances are 4x as accurate as a chain then the design is worse; considering there are 6x as many gear-to-gear interfaces.

 

..."...4x as accurate as a chain..."? In what context are you talking about accuracy? Cam timing? Chains whip, and can have unwanted harmonic side effects, as can belts. What tensioning systems are you describing for your superior belt drives?

 

This could be argued in several ways but I set upon this 4x/6x example to show the uselessness of your assertions without real data or even accurate descriptions of differences between systems.

 

What "data" would you like to see exactly? It seems to me that we are both dealing in theoretical generalities here. You're effectively saying that the OSG gear drive setup is garbage, I'm saying that it's probably not. Presumably - according to your definitions - you would consider the chain driven version of the TC24 B1 to be 'superior' to the gear driven version? You think they should have made a belt driven version - yes?

 

I would assert that a belt is a better way for a lot of reasons.

 

I look forward to seeing the 'BJHines Engineering' aftermarket conversion kit which provides a belt driven alternative to all those flappy chains and "inaccurate" gear drives out there in the world of performance engines.

 

The OSG TC24 is a compromise by its very nature; There's not much scope to work around the fact that it's based on what is essentially a mid-Sixties block design ( which made me laugh at your "antique" comment ). I think they've done very well to work around the limitations of that block ( especially around the water pump area ) and their stuff clearly works.

 

 

 

 

It's all moot anyway. One of the big factors that you can't put a number on is the WOW factor, and it will help sell the product. Apart from any performance gains, it all looks rather cool, rather impressive, and - a big deal this one - straight cut gear drives just plain sound nice.

 

Try pitching dialectic physics against "it sounds nice" and see who wins...

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Disclaimer: I know nothing about gear drives nor belt drives nor chain drives.

 

It seems to me the advantage of a belt drive would be it's quietness. I recall reading stuff about the VK56 using belts to reduce NVH, and nissan talking that up (http://papers.sae.org/2004-01-0985/ available here: http://www.titantalk.com/forums/attachments/titan-general-discussion/9430-endurance-5.6l-attachment.pdf).

 

I'd love to see some people link to actual engineering articles that address these issues, as I'm sure they have been studied in depth. Actual information would be great, in preference to opposing and repeated opinion-based posts.

 

Thanks,

 

Dave

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I am only counting the interfaces that add up to total SLOP! most of the other engines you have shown have a lot of gears but not a lot of driven interfaces from crank to each cam. The bloody antique Cosworth V-8 needed an external valve-train damper to keep the teeth from breaking off the goofy gears.

 

As I have clearly pointed out and you have confirmed; the wacky, OSG, L-engine, gear-drive is a workaround for form over function.

 

There are good reasons for the gear drive over other possible designs. OIL is key, and easy compact design so that it works with most stock component placements.

 

1. A belt cannot run in the oil environment of the front cover. It is a harder workaround to "DRY OUT" the front cover for a synthetic, organic belt drive, or to move the drive further forward, outside the front cover.

 

2. A twin-cam, 2 stage, chain drive requires multiple tensioners usually driven by oil pressure. The hardware and plumbing to tension a wet, twin-cam, chain drive would be a lot bulkier and more external than allowable due to the target market demands.

 

3. The gear drive is compact, fits within the footprint of the original design, and is a wacky, goofy, trouble-prone, compromise at best.

Edited by bjhines
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Actual information would be great, in preference to opposing and repeated opinion-based posts.

 

Don't look at me if you want numbers. I don't think anyone else - except perhaps OSG themselves - is going to be able to give you the kind of stats you seem to be asking for. Exactly how would you compare the chain-driven TC24-B1 with the gear-driven TC24-B1Z, except in terms of cam timing stability, longevity and - abstracts these - visual wow factor and audible 'me gusta'...?

 

Can you tell me what bjhines is saying? I read his posts, but don't seem to be able to find a tangible point ( except perhaps something along the lines of 'it's garbage' ). I've got a hunch that the gear-driven version of the TC24 controls the relationship between the crank and the camshafts a lot better than the chain-driven version, but I can't give you any numbers. However, looking at the amount of high performance / race engines ( many of which are clean-sheet, from scratch, designs ) which used multiple gear drives in the past, I'm betting that their limitations are far outweighed by their advantages.

 

But like I said before, all this blue sky theory is moot. The TC24-B1Z is a niche market product, and a compromise by its very nature. If anyone wants to judge it on pure engineering theory then they are very probably missing the point...

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The TC24-B1 with chain drive suffered from the harmonic interaction between the cams driven by a single chain, with a single tensioner. A much better way of dealing with timing chain drive is to use a 2-stage chain drive where ONE cam is driven by the main chain, and the OTHER CAM is driven by a shorter(independently tensioned), chain between them. There is just not enough room in the front of the L-engine to allow original component placements in the engine bay with a 2-stage chain drive.

 

Sooooo... The entire IDEA of this aftermarket attempt at cool-factor Zeta garbage is a waste of time. Put a cheap-rebuilt BMW M-50-L6 in there and you get a PROPERLY designed twin-cam engine, not a silly waste of aluminum and money.

Edited by bjhines
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The TC24-B1 with chain drive suffered from the harmonic interaction between the cams driven by a single chain, with a single tensioner.

 

And your source for this information about cam harmonics in the TC24-B1 is? First I've heard of it.

 

I've got two old Nissan engines that are 24 valve, twin cam straight sixes. The cams are driven off the crank by a single duplex chain, and with just one ( manually adjusted ) jockey-wheel tensioner. It's a design that has been around a long time, won a lot of races in period, and has a reputation for being pretty much bullet proof. You reckon they are garbage, I take it?

 

 

Sooooo... The entire IDEA of this aftermarket attempt at cool-factor Zeta garbage is a waste of time. Put a cheap-rebuilt BMW M-50-L6 in there and you get a PROPERLY designed twin-cam engine, not a silly waste of aluminum and money.

 

I think the "waste of aluminum and money" trumps the BMW M50 ( coughVANOScough ) in an S30-series body for me. Although I can think of other, perhaps more appropriate and interesting, donks to stick in there. I wouldn't kick a freebie TC24-B1 or B1Z out of bed though...

 

 

 

"Zeta"? You've lost me there ( ??? ).

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Hey John,

 

I hope you don't mind me keeping the topic going, I just wanted to add another data point, that being the LZ twin cam Nissan heads.

 

From what I can gather, they used a combination of both things being discussed: a gear drive, then a chain to drive both the cams. I found some great info on a now-deceased website run by Errol Smith in Oz: http://web.archive.org/web/20091030075820/http://www.datrats.com.au/lz_twin_cams.htm Specifically these pics I found interesting:

 

I'm going to save and attach them here for posterity.

post-1220-047358200 1333474274_thumb.jpg

post-1220-073029600 1333474273_thumb.jpg

post-1220-038023900 1333474270_thumb.jpg

post-1220-052357700 1333474269_thumb.jpg

post-1220-002204500 1333474273_thumb.jpg

post-1220-050186100 1333474272_thumb.jpg

post-1220-070720300 1333474271_thumb.jpg

post-1220-097175100 1333474270_thumb.jpg

 

Given this solution clearly works for a L-series, I wonder why OSG decided against it. Someone wanna email them a link to this thread? It'd be great if more companies were available and/or willing to provide actual information to the *gasp* interwebs.

 

Dave

 

PS. Alan, I'm sure you have more info/pics on the LZ, would love to see them. Oh and when I asked for information, I was referring to gear versus chain drive in general, not specifically for the L-series. I should have been more clear.

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Yes, the Nissan answer to DOHC involved gear drives on the LZ Series as Helix Mentions. Remember this head was designed during the engine's CURRENT PRODUCTION RUN as well.

Updating the design with componentry which fits within the envelope provided...

And as Alan mentions, as an owner of a couple of S20 engines, it is to be noted that OSG manufactures this same drive configuration as an UPDATE/RETROFIT to that engine's proven competition record (and known issues.)

 

When you have an existing design, you work with what you have. I don't see a lot of people making belt-drive conversions for the L-Engine. They make them for the SBC, though.

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I wondered the same thing at first, but knew I'd seen similar in motorcycle engines so I looked around and sure enough it seems that MOST high hp motorcycle engines using timing gear arrangements that are quite similar. Granted those engines go 20-40k between overhauls... I'd imagine that as long as they kept the gears well lubricated they shouldn't wear any worse than transmission gears, but I am quite curious how well they're getting oiled and what start up wear is going to be like on them.

 

Honda motorcycles has had gear driven cams in a few of their v-4 race biked like the rc30 and rc45. Their latest was the RC-51 1000cc twin. Now on the the timing accuracy... The idler gears are split- like two gear halves stacked together. Take a gear and lay it on a table. Now take another duplicate and lay it on top but rotate it a degree or so. Thats the concept. There is a few springs that keep the gear halves indexed with a degree or two difference. When everything is assembled the idler gears are straight and aligned by the teeth of the drive and cam gears but with spring tension trying to spread the idler gear a few degrees apart... It maintains a no slop drive train. As the gears and engine heats up and dimensions change, the idler gears contiuously take up the slack.

Hope that clears up the question

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Honda motorcycles has had gear driven cams in a few of their v-4 race biked like the rc30 and rc45. Their latest was the RC-51 1000cc twin. Now on the the timing accuracy... The idler gears are split- like two gear halves stacked together. Take a gear and lay it on a table. Now take another duplicate and lay it on top but rotate it a degree or so. Thats the concept. There is a few springs that keep the gear halves indexed with a degree or two difference. When everything is assembled the idler gears are straight and aligned by the teeth of the drive and cam gears but with spring tension trying to spread the idler gear a few degrees apart... It maintains a no slop drive train. As the gears and engine heats up and dimensions change, the idler gears contiuously take up the slack.

Hope that clears up the question

 

I've seen this in a Toyota Steel 5 speed, about 20 years ago, but it was not a 1/2, 1/2 split gear, it was 1/4, 3/4 setup, ( I assumed it was to take up any slack / backlash )

 

Nigel

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Nigel I believe the Honda bikes are all 3/4-1/4 also. Half and half was to simplifiy description. Thanks for the follow up. What Toyota was that on and what application?

 

Toyota Celica, I can not tell you the year though.

 

Like this

post-2090-080844100 1334196273_thumb.jpg

Edited by Noddle
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My 1975 Toyota Corona had a cast iron main case as well. I think most toyotas of that era used that tranny.

 

Not all of them had the type of gear I was talking about, the 3 I had, only 1 had the split gear.

I ran it behind a ford 250 xflow with a castlemain bellhousing in my XK falcon

Edited by Noddle
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