David Vizard Interview - Port Velocity Dyno Tests

[David Vizard]

Rwdfords said:

Hello David,
I would be very interested to hear the specification of this engine, looking at the torque curve it is like nothing I have every seen for the 2.0 pinto engine, the low rpm torque is massively higher, I have only ever seen one dyno graph with a higher peak torque value than this and that was from a 220bhp tarmac rally engine but obviously much more of a peak hp tuned engine than this one on TB's and full management

How have you managed to get such an impressive torque curve with 45's and a low duration cam with not a lot of lift? Very impressive to say the least

If you could remember any of the other engine specs it would be very useful to me, the more detail the better, particularly the head flow, cam LSA, duration @.010" and .050" with lash, exhaust specs, intake length, choke diameter.....

Regards
Jason

Jason,

Cannot remember all the specs of the engine but I can address the torque aspect of your question. First valve events are very important - closing the intake too late cuts torque. Cam had very high lift - can't remember exactly that's why I said about 0.500. On reflection that may have been one of the engines i tested different follower designs so the lift could have been as much as 0.580 or so but for sure but was well over 0.500. Used 4-2-1 exhaust - that was worth 30 (yes 30) lbs-ft of low speed torque over a 4-1. Also good cylinder seal and high cranking pressure as a result of the CR and valve events. Also used Dellorto DHLA carbs as they are worth low speed torque. I think we also used longer intake trumpets with less than a normal taper. Also that low speed torque was helped a lot by swirl, good mixture quality and a really strong spark at just the right time.

Funny you should think that was a good torque figure for a 2 liter engine. I also did at the time but having seen what a 2 liter BTCC engine of just a couple of years back could put out it does not look that good anymore.
Had an RS 2000 with a 10.9/1 170 hp motor like this (2085 cc. Was really nice to drive. - would pull from about 2000 rpm strongly and came on hard by 3000. Also would smoke the tires big time in 1st.

[Rwdfords]

Hello David

Thank for your reply

The high lift figures have said with such low duration make perfect sense to me looking at how much low to mid rpm torque that engine had, interesting how much extra low rpm torque the 4-2-1 manifold made, would perform really well out and away from corners

About the cam timing events, can you remember what sort of LSA you used with this and your best pinto engines with high lift short duration cams?

We have used many different LSA's with ones of around 108 to 112* seeming to work best with short timing cams around 285* to 295* maximum at .001" lift, I am thinking 108 to 111* would give best power from 3000 to 8000rpm, does this LSA appear correct to you or is this a little too wide?
Your mini bible LSA vs valve size and cylinder cc chart is giving me 110* LSA with a 46mm inlet valve


About mixture quality we have tried a variation of Somender Singh grooves with shallow rather than deep grooves and a very tight .030" squish giving a light brown burn pattern covering almost all of the piston crowns and in the grooves, is this something you aim for with your engines and have you experimented with grooves, dimples etc to get a more complete burn?

Using a tight squish and no grooves seems to cut off flame travel in the squish areas until the piston has moved further down the bore


I still think your torque figure is very impressive, the BTCC engine would have been 4V per cylinder with much more inlet flow, not quite the same achievement as working miracles with an old 2v engine that was probably designed in the 60's in my view

Regards
Jason

[David Vizard]

Rwdfords said:

Hello David

Thank for your reply

The high lift figures have said with such low duration make perfect sense to me looking at how much low to mid rpm torque that engine had, interesting how much extra low rpm torque the 4-2-1 manifold made, would perform really well out and away from corners

About the cam timing events, can you remember what sort of LSA you used with this and your best pinto engines with high lift short duration cams?

We have used many different LSA's with ones of around 108 to 112* seeming to work best with short timing cams around 285* to 295* maximum at .001" lift, I am thinking 108 to 111* would give best power from 3000 to 8000rpm, does this LSA appear correct to you or is this a little too wide?
Your mini bible LSA vs valve size and cylinder cc chart is giving me 110* LSA with a 46mm inlet valve


About mixture quality we have tried a variation of Somender Singh grooves with shallow rather than deep grooves and a very tight .030" squish giving a light brown burn pattern covering almost all of the piston crowns and in the grooves, is this something you aim for with your engines and have you experimented with grooves, dimples etc to get a more complete burn?

Using a tight squish and no grooves seems to cut off flame travel in the squish areas until the piston has moved further down the bore


I still think your torque figure is very impressive, the BTCC engine would have been 4V per cylinder with much more inlet flow, not quite the same achievement as working miracles with an old 2v engine that was probably designed in the 60's in my view

Regards
Jason

Jason,
As far as I can remember I used 108 LCA for CR's of about 10/1 and thus widened to 110 - 111 when the CR went to 14.5/1 (or there abouts.
I have not tried the sigh grooves yey. I would like to see some true back to back numbers before I screw up a set of heads well into the 4 figure number. What can you tell us here??
DV

[Rwdfords]

Hello David

Thank you for the LSA vs SCR figures

About the grooves I do not have any back to back power tests but I do have pictures showing the combustion pattern covering almost all of the piston crown, which I have not seen before with this engine (and many other 2v engines) when using a tight squish clearance .040" or less, I would rather not post pictures of this on a forum but I would be more than happy to email some high quality pictures on to you and groove dimensions, my address is: [e-mail]

What I can say is there is no risk of damage with this grooving method, it could be tested on any engine quite easily

Regards
Jason

[anonymous-user]

Apparently, according to the Mr. Singh, 9% of fuel injected into an engine is not burnt, but ends up in the exhaust (2%) and the sump (7%).

Really? that would mean after my car had used a tank of 65 litres i would have 4.55 extra litres of fluid in my sump..........

(except of course it would be fuel vapour and so it would get ingested by the PCB system and straight back into the engine to be burnt)


Having spent a couple of years optimising squish zones for WRC engines (which are the most detonation prone engine ever (>12:1 CR, 3.5bar boost abs. + massive EBP due to the poor turbine pressure ratio brought on by the inlet restrictor)) and having recently been part of a "crevice volume" optimisation project (£1.2M spent) it sounds like those groooves are just a "poor mans" tapered squish zone.........


(BTW, simply check out the "engine out" THc emissions for a modern pent roof 4V'er and you have all the info you need on unburned mass fraction (and i'll give you a clue, it aint 9% ;-)

[Rwdfords]

Max
I am not in favour of "Singh grooves" or any claims posted on his website, what I am in favour of is burning all of the mixture in the combustion chamber as quickly as possible in a controlled manner, with most 2v engines there are large flat squish areas and a plug which cannot be placed right in the centre of the chamber as with 4v engines

With 2v engines using a tight squish .040" or less I believe the flame front has a hard time getting into the squish areas right out to the bore line when the piston is near tdc, it appears the flame front cannot reach these areas until the piston has moved considerably down the bore, by that time usable power has been lost

4v chambers are very different than 2v, the maximum advance needed is far less than that needed with 2v engines, they have a faster burn rate, 2v NA engines need all the help they can get imho in this area

I think it is best to be open to new ideas, try new things and see what works best for you

Regards
Jason

[David Vizard]

Max_Torque said:

Having spent a couple of years optimising squish zones for WRC engines (which are the most detonation prone engine ever (>12:1 CR, 3.5bar boost abs. + massive EBP due to the poor turbine pressure ratio brought on by the inlet restrictor)) and having recently been part of a "crevice volume" optimisation project (£1.2M spent) it sounds like those groooves are just a "poor mans" tapered squish zone.........

Funny you should say that. I have only recently come to a tentative conclusion that every two valve engine quench area I have ever seen including mine are not what they should be - not even close. AS for crevice volumes did you not mean minimizing rather than optimizing???

As of now I am into some CFD stuff on what happens in the quench but I fear the stuff I have access to is not up to what I might need.
what I can say for almost sure is that the way most people think Singh grooves function (whether they work or not) is not really what happens.

As of now I am pretty certain i still need to learn a lot here before i start telling others how and what certain quench pad modifications actually do. I am open here to any info that might fill in some of the gaps in what I am working on.

DV

[Rwdfords]

Here is a good article on piston crown shapes, the theory is that these modifications increase mixture motion and or swirl approaching tdc with grooves & dimples to help mixture quality and agitation creating eddies, which can also help with low lift flow (by creating a boundary layer) with raised top pistons and also mixture quality in the squish areas by keeping the fuel/air mixture moving and in suspension rather than fuel dropping out and not being burned

http://www.circletrack.com/techarticles/piston_tec...

Any darker area on the chamber or on piston crown is said to be where fuel is dropping out of suspension and is not being properly burned, supposedly an ideal chamber burn pattern would be one with is light brown right across the piston crown/chamber all the way to the bore line, this would indicate a very good clean burn with no fuel being wasted

It makes sense to me that such a burn pattern would indicate good fuel atomisation, mixture motion and a fast burn needing less total ignition timing for best power/torque, if anything was not working well it would show up as a dark area on the chamber/piston face

4v engines have a much better central plug location, most of the chamber volume being close to the centre of the cylinder with a tight + narrow squish band all around the bore, to me this looks a lot closer to an ideal shape than a 2v chamber, burn patterns and total ignition timing needed with each chamber shape seem to confirm this

It would be very interesting to here your theories on this David, I may be completely wrong in my observations but it does appear such modifications could offer an advantage

Regards
Jason

[SWR Performance]

Stan Weiss said:

Thanks Tony, while I would think that I will see many of the same topics here as on Speetalk, I would hope that some of the views will be from a different prospectus. Not all SBC, BBC etc.

Stan

Nice to see fellow SpeedTalkers here... ..and I second that notion, Stan. I have had enough SBC tuning for a while. Btw, I am Bjørn, aka the Moderator known as "SWR" from Speedtalk. That handle was taken here so I added a little to mine. Hopefully it will not get me shot down, I saw something about not using a company name after making it...

[David Vizard]

SWR Performance said:

Nice to see fellow SpeedTalkers here... ..and I second that notion, Stan. I have had enough SBC tuning for a while. Btw, I am Bjørn, aka the Moderator known as "SWR" from Speedtalk. That handle was taken here so I added a little to mine. Hopefully it will not get me shot down, I saw something about not using a company name after making it...

Bjorn, are you the Bjorn that is coming to my September seminar at Swansea with a couple of friends??
DV

[David Vizard]

Rwdfords said:

Here is a good article on piston crown shapes, the theory is that these modifications increase mixture motion and or swirl approaching tdc with grooves & dimples to help mixture quality and agitation creating eddies, which can also help with low lift flow (by creating a boundary layer) with raised top pistons and also mixture quality in the squish areas by keeping the fuel/air mixture moving and in suspension rather than fuel dropping out and not being burned

http://www.circletrack.com/techarticles/piston_tec...

Any darker area on the chamber or on piston crown is said to be where fuel is dropping out of suspension and is not being properly burned, supposedly an ideal chamber burn pattern would be one with is light brown right across the piston crown/chamber all the way to the bore line, this would indicate a very good clean burn with no fuel being wasted

It makes sense to me that such a burn pattern would indicate good fuel atomisation, mixture motion and a fast burn needing less total ignition timing for best power/torque, if anything was not working well it would show up as a dark area on the chamber/piston face

4v engines have a much better central plug location, most of the chamber volume being close to the centre of the cylinder with a tight + narrow squish band all around the bore, to me this looks a lot closer to an ideal shape than a 2v chamber, burn patterns and total ignition timing needed with each chamber shape seem to confirm this

It would be very interesting to here your theories on this David, I may be completely wrong in my observations but it does appear such modifications could offer an advantage

Regards
Jason

Jason,
My fellow tech writer Jim McFarland wrote that story. Has some good info if anyone feels they need to bone up on this subject.
As you staed the burn pattern need to be no pattern but a complete near even coloring of the crown. Getting that is not alway easy but it alweays seems to pay dividends.

One point though is that a centrally place plug is not always best at firing of the charge. A 5 port Mini combustion chamber is (surprise surprise) actually better than most 4 valve heads in terms of effective combustion.

BTW tried those dimples - the better the car/injection atomization the less the dimple do.
DV

[SWR Performance]

David Vizard said:

Bjorn, are you the Bjorn that is coming to my September seminar at Swansea with a couple of friends??
DV

Yes David, that's me. We are currently two, but if all of the ones I mentioned it to that showed considerable interest can go - / make time for it / drop everything on the spot - and come we'll turn out to be 5.

[SWR Performance]

David Vizard said:

One point though is that a centrally place plug is not always best at firing of the charge. A 5 port Mini combustion chamber is (surprise surprise) actually better than most 4 valve heads in terms of effective combustion.

I - for one - would venture to guess that not many know that certain, rather recent, F1 engines saw over 50º ignition lead to make power, and the much-fabled Yamaha FZR- and YZF-series 5-valve heads in race tune - race kit ECU - saw 47º of lead at 12 000 rpm... They also took a LOT of compression without detonating, one specific example we made was a BIG-bore FZR1000 of 1990 vintage, sporting 1183cc with offset pistons and - obviously - billet cylinder block. It ran 14.2:1 static CR on regular 98RON pump gas, stock road bike ECU with some 40º of ignition at 11 000 rpm. And a squish clearance most said would kill it right away. I still hear people say that CR value cannot be correct, but it ran like that for years. And won.

[The Excession]

SWR Performance said:

That handle was taken here so I added a little to mine. Hopefully it will not get me shot down, I saw something about not using a company name after making it...

You can change your name easily by editing your profile. All though in this quiet corner of PH it might not get noticed, if you start posting in other areas you will be asked to change it.

HTH and welcome to PH!

[chuntington101]

SWR Performance said:

I - for one - would venture to guess that not many know that certain, rather recent, F1 engines saw over 50º ignition lead to make power, and the much-fabled Yamaha FZR- and YZF-series 5-valve heads in race tune - race kit ECU - saw 47º of lead at 12 000 rpm... They also took a LOT of compression without detonating, one specific example we made was a BIG-bore FZR1000 of 1990 vintage, sporting 1183cc with offset pistons and - obviously - billet cylinder block. It ran 14.2:1 static CR on regular 98RON pump gas, stock road bike ECU with some 40º of ignition at 11 000 rpm. And a squish clearance most said would kill it right away. I still hear people say that CR value cannot be correct, but it ran like that for years. And won.

So what enabled them to run soo much advance and comp. ratio?... was its just the squish that enabled it?

[SWR Performance]

chuntington101 said:

So what enabled them to run soo much advance and comp. ratio?... was its just the squish that enabled it?

No, it didn't ENABLE us to run it... it needed that advance to make power, those chambers have a really slow burn.. They flow a ton, but the burn caractheristics are "less than desireable" to say the least. Most anything you can do to induce some charge motion in a 4- or 5-V chamber to promote burn speed will in most instances net you a power gain, often even if the flow values DROP marginally from stock... They often flow enough to make 200+ hp looking at airflow alone but make 150 hp and need 40+º of advance to make those 150hp, that's a real pointer right there.

[tony g]

SWR Performance said:

Stan Weiss said:

Thanks Tony, while I would think that I will see many of the same topics here as on Speetalk, I would hope that some of the views will be from a different prospectus. Not all SBC, BBC etc.

Stan

Nice to see fellow SpeedTalkers here... ..and I second that notion, Stan. I have had enough SBC tuning for a while. Btw, I am Bjørn, aka the Moderator known as "SWR" from Speedtalk. That handle was taken here so I added a little to mine. Hopefully it will not get me shot down, I saw something about not using a company name after making it...

Welcome to you too Bjorn
ps I would love to have you build me an inlet manifold Leimann style for my Evo motor ....one day one day


Tony

[SWR Performance]

tony g said:

Welcome to you too Bjorn
ps I would love to have you build me an inlet manifold Leimann style for my Evo motor ....one day one day


Tony

Thank you Tony (and The Excession) for welcoming me here. Just let me know, can do that on a weeks notice or less..

[Pumaracing]

Stan Weiss said:

DV:- Yes – in there I show how to build a pro result bench for about $150 or less. Funny when I think how easy this is I always end up re-calling a story about Bill Blydenstien. Bill, who I personally know and greatly respect, won the British Touring Car Championship - back in the 50’s I believe. In a feature about his engine shop a motoring journalist made quite a deal about Bill’s technique to flow heads with water. I always wondered why do it the hard way but I never got around to asking him that.

You say "know" and "respect" but sadly Bill went to the great engine workshop in the sky a few years ago so "knew" and "respected" might be more applicable. I really liked old Bill. He had a no-nonsense approach to head modifying. He always said that most of what most head modifiers did made the head worse not better. That only the critical areas needed working on and that all the shine and polish made no effing difference whatsoever. A few years ago I promised to go round and have another cup of tea and a chat but I left it too late. I still have a head he gave me for flow testing purposes but I doubt he wants it back now.

[David Vizard]

Pumaracing said:

You say "know" and "respect" but sadly Bill went to the great engine workshop in the sky a few years ago so "knew" and "respected" might be more applicable. I really liked old Bill. He had a no-nonsense approach to head modifying. He always said that most of what most head modifiers did made the head worse not better. That only the critical areas needed working on and that all the shine and polish made no effing difference whatsoever. A few years ago I promised to go round and have another cup of tea and a chat but I left it too late. I still have a head he gave me for flow testing purposes but I doubt he wants it back now.

Dave,
Where on earth was I when that happened. That's a hard pill to swallow. I had absolutely no idea Bill had gone. That's you and me both who are going to miss out by not being able to visit. One of the nicest guys I ever knew. A real gentleman to be sure.

DV

PS got that new phone # yet?????