Wedge vs Crossflow
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  1. #1
    Fellow Frogger! sapito's Avatar
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    Default Wedge vs Crossflow

    Ive looked everywhere guys and cant seem to find a discussion about this.
    Im wondering what mods could be done to the wedge r18 head and what figures some if any have had using it instead of the crossflow?
    The r18 engine is similar layout and design surprisingly to the fiat version with also a high position camshaft.
    How big could I go with the ports and valves?
    Ive looked at some cross section figures and it seems that the wedge has the waterjackets close to the ports.
    On the datsun A series pushrod the wedge head can take 40mm valves.
    Would the bigger bore allow for a bigger valve on the r18s head design?
    Hope I dont offend anyone as the crossflow is an incredible design.
    Dodge have proven the hemi is a force to be reckoned with with their new design with twin spark plugs and other factors check this link its very interesting reading.....
    http://www.popularhotrodding.com/tech/0403phr_hemi/
    Wedge vs crossflow which is best for reliability and street and track performance?

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  2. #2
    1000+ Posts PeterT's Avatar
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    Default

    I think there's good and bad examples of both. I thought I new a bit until having a 205 head modified recently. The head guru was keen to remove any dead areas in the chamber. Basic comment was the 205 was hard to get right as it's fundamentally wrong. There's heaps to consider; valve flow rate ratios, valve diameter to lift ratio, swirl, etc. Latest thought, is a small chamber with a matching area in the piston. Good luck!

    '92 205 Mi16
    '90 Mi16x4

  3. #3
    1000+ Posts alan moore's Avatar
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    Default

    The crossflow is so far ahead of the wedge in Renaults that only a true fanatic would try. Saying that I built a hot wedge motor for a Europa, 18 months ago. The car had been modified by Geoghens (spelling) from new, and he wanted to keep it basically the way it was made.

    I had told him that 110 Hp would be the best he could hope for even after making it a 1565 instead of 1470cc. He had faith it would be better, given he had seen the performance of various other motors I had built.

    Anyway, it made 105Hp at the wheels equating to about 135Hp. Best of all, it is now faster than other Lotus club members crossflows with twin Webers. I still think that dyno reads high.

    Saying that, a good crossflow will always beat a good wedge, at least in Renaults, valve shrouding being the limiting factor of a wedge.
    '56 Renault 750 (16TS Power)
    '62 Renault Dauphine Gordini
    '89 Renault Alpine GTA V6 Turbo
    '08 Renault Megane sedan

  4. #4
    Fellow Frogger! sapito's Avatar
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    Default wedge performance

    Can you tell me what size webers, what manifolds are available and other factors to get this power you made (cam specs?). The reason being is that My Nissan A series makes 84kws at the wheels and the best Nissan A built by JTS (A specialist of A series for open wheelers) gets around 160-170hp at the engine and some Japanese have made 200+ with the 1607cc (bore limit 79mm with 82mm stroke) and all with the wedge head design. Of course it all depends on the dyno but 160-170 at the engine is a proven figure. The nissan wedge is assisted by a hi port design and maximum valve size is 40mm inlet with the 1300cc formula 3 engine
    Heres the link and check the 155hp engine at the bottom of page..
    http://www.datrats.com.au/A13RACE.htm

    With the bigger 300cc extra capacity bore size an extra 15hp is not uncommon from these antiquated but heavy little things.

    Here are the finish on the wedge head and the hi port pics



    Last edited by sapito; 29th April 2004 at 12:28 AM.

  5. #5
    1000+ Posts Luca's Avatar
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    Who did your head work?

  6. #6
    Fellow Frogger! sapito's Avatar
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    Default wedge

    Sorry this aint my engine.
    I dont know if this is good or not as I dont understand how to make this things perform to their optimum efficiency.
    However Alan for JTS in sydney knows apparantely how to squeeze every last little pony out of the wedge. There are certain things to be done to them to get the right swirl and other necessary characteristics.
    However if you look at he link the owner Errol or Feral as he prefers bought this engine from JTS.

  7. #7
    1000+ Posts alan moore's Avatar
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    Default

    The Lotus head had siamized inlets and ran a ported standard manifold, ported head, bigger valves, better springs, an XE Falcon downdraft Weber and some nice extractors. Ivan Tighe 154 cam. about 400 thou lift, 10.5 Comp ratio flat pistons, and a much uglier chamber than the one above. I don't remember any other sizes as such. I wanted to fit a side draft Weber, but he was talked out of it.

    It does definately go, it was just I was surprised particularly considering how ordinary I thought the head design was.
    '56 Renault 750 (16TS Power)
    '62 Renault Dauphine Gordini
    '89 Renault Alpine GTA V6 Turbo
    '08 Renault Megane sedan

  8. #8
    Fellow Frogger! sapito's Avatar
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    Default r18 wedge

    So if everything was done to the wedge like done to the crossflow engine do you think alan youd be nocking at 160hp?
    It seems reasonable considering the fiat 1600 OHV can and its a direct copy of the r18 but without the alloy block and fitted to mid 70s to 80s cars to adhere to pollution laws in some countries Id guess.
    d.

  9. #9
    1000+ Posts alan moore's Avatar
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    Renault talk about 160Hp from their hot crossflows (SAE Shetland Hp). I think you would be doing well to get 130 out of a street useable wedge. That Europa motor was actually fairly hot, and it gets difficult to find more after that without resorting to a huge cam, comp and Avgas.
    '56 Renault 750 (16TS Power)
    '62 Renault Dauphine Gordini
    '89 Renault Alpine GTA V6 Turbo
    '08 Renault Megane sedan

  10. #10
    Fellow Frogger! sapito's Avatar
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    Default Wedgey

    Well Ive almost given up in finding or getting the 42mm inlet crossflow head and decided to mod a wedge engine. Will run twin 44mm mikuni sidedrafts a suitable cam for the 10.5 compression and plenty of headwork and bigger valves.

    Alan if your wedge client made 105hp at the wheels with a single downdraft wouldnt some twin 45s, more head work and suitable cam be able to achieve more ponies??

  11. #11
    1000+ Posts alan moore's Avatar
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    Bigger inlet seats can be fitted to the crossflow, or the std ones machined out will just take 42mm valves. I saw one with bigger seats and R25 44mm valves fitted recently. This car (R12)is currently winning the under 1600cc class at Mt Cotton hillclimb in QLD against much newer multivalve opposition.

    A good crossflow Renault will always beat a good wedge. They simply flow much better, with less valve shrouding and much better ports to start with.

    That Lotus head had only two inlet ports , so only a single sidedraft could have been fitted. Barring titanium valves and retainers, no more could have been done to it using 98 octane fuel.
    Last edited by alan moore; 6th October 2004 at 03:07 PM.
    '56 Renault 750 (16TS Power)
    '62 Renault Dauphine Gordini
    '89 Renault Alpine GTA V6 Turbo
    '08 Renault Megane sedan

  12. #12
    Fellow Frogger! sapito's Avatar
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    Default Crossflowing

    Then crossflow it is thank you.

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