http://www.billzilla.org/2v4vpage2.htm Toward the bottom of the page there is a discussion about the designs of 8v vs 16v vs 20v head designs and the potential power that can be extracted from the same capacity engines with the different heads. It would appear that a 20v design is actually less efficient compared to a 16v which is said to be the most efficient based on flow rates and air speed. It suggests that the 20v has a worse flow rate as the valves are too close together and there isnt enough surface area. Also there is a chart showing how 8 an 16v develop power at different stages and most interestingly is the 16v have more TORQUE lower down the rev range than a 8v and surprise* more power throughout the rev range and still holds its torque higher up the rev range. I must admit i dont know a massive amount about head designs and flow rates just that ive had 8 an 16v and know that without a second thought i would pick 16v all day long but i am interested in the idea of a NA 20v conversion as ive seen ones running c200hp. Please discuss. stands back and observes the inevitable can of worms about to expload
I often thought about whether your could make a NA 20v ABF, and wether it would make good power?? Also, does a 20v become better when you have forced induction??
Depends on how you define better. Bill is not far off the mark GENERALLY! 3K OHV Toyota engine from 1969-77 = 1200cc runs on carbs, breaker points, is a a counter flow head design and found on old KE20 Corollas with 50ps and 52lbft. They work very well when STD and sold millions! G13 Suzuki DOHC EFI motor from the late 80s and early 90s = 100bhp@6800rpm. It is only obious that old engine will have to have lots of dev works to improve BMEP over a range of RPM to compare with an already improved STD engine. Not a fair comparison. a bit like comparing a Type 1 1588cc single port Beetle engine mod list, with a modification list from a Subaru EJ20 motor. Thought it would have also been best to compare a BDA motor with a 'Kent' Crossflow. Rather than a K series Rover motor. Again the age gap, orignal purpose and OEM requirements at the time tends to be ignored.
there is a n/a 20v engine fitted to some passats but its not a very good engine. but with a bit of work i think it could be decent
There is no question a 16V will make more power and torque than an 8V. The interesting comparison is 16V vs 20V. Personally I think 20V was a fad, if it was that much better than 16V there would be more 20V engines in top end motorsport. The 20V has lots of valve area but suffers from fragility at high revs, hard to get the CR high, small cam followers limiting ultimate cam profiles etc etc Although they have been used on bikes, 20vs are not on many of the top power monsters so I question whether they are needed
toyotec with the master class- i get the impression you maybe know the guy who wrote that feature? yes i agree it does show how far engines have come that you can extract such power from small capacities but needing such high revs - 10.5K revs is crazy for any kind of engine for daily use. I just found it interesting what he says about how F1 teams tried to develop 5v more but gave up and even in production cars now 5v set up is quite unusual and was keen to figure why. you guys are right, there is a NA 20v available from factory. Il find some more details but im sure ive seen some running ITBs pushing 200hp and just thought it was something a little different.
yamaha were very into the 5 valve, but i think the new direct injection/fsi stuff doesn't leave any room for 5 valves
Didn't proton or one of the far-eastern marques mess with 3 valves per cylinder? I wonder how that worked out..
My mate runs a 2.ol 20v on itb-s in a mk1 and has round 200 hp Cams are 272-s i think not sure and mildly ported head Goes like stink! He gives it beans 110% at every track day for past few years and never had a problem or failure Very very quick mk1 round any track Cant find a pic now, its a black mk1 with big green number on the door think its 33
I suspect the 5 v per cylinder was mostly an emissions exercise and there was a mk1 with 2 ltr,s and 20v head and t/b,s that claimed nearly 200bhp or thereabouts at the wheels if my memory is correct.
A little bit more than claimed bud. The ex mad20v (now owned by Paul "boff" Morris on here) MK1 made a genuine 208hp at the wheels (240hp at the flywheel), and goes rather well.. Whilst a 20v engine certainly has more valve area, the are issues with cam bucket diameter limiting the duration and lift, plus the layout of the valves lead to less than ideal airflow motion & poor combustion. What's gained in one area is compromised in others.
