help chooseing 20VT engine for URQ

[diesel des]

Hi people I am new to this forum and have been diverted here from a 20VT mail list. I have looked at the posts and there seems to be lots of very smart people here that no a 20VT inside out. I hope you can help a newbe with some questions i have and give me some good advice. I have always wanted a fast URQ. To me fast means 400-500 bhp.

I have got a 84WR that needs a little body attention parked at my garage. I fitted new (hydraulic shop) oil cooler lines as the old ones where duff and got the old girl running. She had been sleeping for 4 years. I haven’t drove the car more that a few hundred yards but already got a bit of a four wheel drift going on, on gravel. These cars are class!

Anyhow a 20VT is what I want under the bonnet of my URQ. I have been looking for the right one for a while now, and two have came at once! I have the option of a more expensive late model s2 ABY or a earlier(cheaper) RR. I have looked through etka and found that the crank, and rods are different. The rods are weaker on the RR I believe. And the ABY has the spark on plug system and the RR has a dissy.

Basically I need to know what is the ultimate tuning potential of both engines, before you need to get into changing rods and other expensive stuff. I want the car for track days and fast road use. I see on this forum that the stock rods give problems over 450 bhp. I could live with stock rods to save cash and stick to 400-450 bhp. I would be using a complete stand alone ECU package. I have also just got a new garret GT30R ball bearing turbo that is good for 500bhp. Im not a great fan of the older technologies that are KKK 26/27. Obviously a custom exhaust manifold will be used. I want reliable power.

How much more is a ABY/ADU engine worth as compared to a RR. Eg twice as much, 50% more?


My previous experience is with 1.9TDI engines. I have one in my Mrk2 golf with 200 BHP. I built that car myself and its quite fast, spanking impretzas etc on a dry day. But even with a quaife it is a nightmare on a wet road. Hence the need for a 4WD for me. I also have a 2.5 L tdi bottom end. Can i use any bits from that to build a big cc 20VT? Obviously the crank could be made fit im sure. Would the diesel rods be a upgrade to 20VT rods?
Please lead me in the right direction once again oh wise ones . Thanks, Des.

[Corey]

With the WR engine, you can fit one of Dialynx's Luminition systems!
It is based around RS2 injectors, a new ecu and a new engine loom.
It totally transforms the 10v motor.
400bhp would be acheivable with a hybrid turbo a different cam and some head work.
Mine is at 320bhp and goes like a dream and I have not lost that mistakable 10v sound!

[diesel des]

I like the 10V sound too, but I just don’t think I would have the nice torque of the 20V Corey. Maybe im wrong.

Anyhow, as far as I can see, the main problem with the 3b/RR is that it has a dissy and therefore misfiring and spark arcing that will bend the rods. What stops you using the coil on plug system from a ABY on an early engine if you are using a stand alone ECU? Or indeed just separate coil packs. Am I missing something here? If I were to do that are both systems about equal in terms of power/rod strength? About 425 bhp on stock rods sounds like a cheep route to me, so if that’s a tried and tested route then im all far it. Thanks all.

[martinjs]

Des, if your wanting 400+ hp from a 3b/rr you'll have to change the rods, think maybe 350 is their limit, its torque whats the limiting factor, mihnea can tell you all about this, it is possible to fit coil packs to these engines, maybe easier to go the aby route though.

martin

[Pisobiker]

Des,
ABY bottom end is known to be good up to 600 Nm peak torque (Mihnea chipped an RS2 ADU engine up to that limit whitout apparent problems so far). I kept my peak torque to 530-540 Nm, however, preferring to stay a little safer expecially because working so close to knock limit of fuel actually available makes things even worst.
Unless someone knows 3B engines have different conrods, then I would say 3B have same peak torque limits as well.
Conrod stresses, apart form fatigue related problems, are much related to peak torque and not peak hp, so that if your engine (and expecially turbocharger) could manage to push 530 Nm all the way up to 7000 rpm, as long as peak torque doesn't exceed maximum safe, conrods should be able to manage more than enaugh for your peak Hp needs. Of course a turbocharger that can provide 530 Nm at 7000 rpm to a 2.2L engine (thus meaning around 530 Hp) will very likely be able to make up to 2.3-2.5 bar peak boost (or even more, meaning a potential of much over 600 Nm peak torque) which you could not manage unless the use of uprated conrods.
Another probelm to be considered is most of conrods failures are related to inertial loads, so max safe rpm needs to be kept whitin resonable limits.

About the use of diesel 2.5 blocks, this is the route I'm trying to take. Still figuring out some final details before starting.


Marco

[diesel des]

Ok, that makes sence its the torque that does the damage. So if i get the ECU to hold the boost back in the mid range to keep torque at the safe range and then let boost rise at the top end to keep the torque flat that will give me the high bhp at the top end. Good stuf. What is the max safe RPM for these engines. EG could you make 500nm at say 7000rpm safely?

[Pisobiker]

Des,
I feel I can say yes. There is no phisical reason I can think of why this shouldn't be correct, apart maybe for fatigue issues.
Most of the concern about those aspects I think might be due to the fact very high output engines (expecially NA ones) deliver max torque at about same rpm as peak Hp, therefore becoming peak Hp the most interesting factor intrinsically taking into account inertial, mechanical and termal loads as well.

And this might also be applyed in some extent to very high perf. forced induction engines, where the pursuit of great top end performances drive to choosing supercharging devices with max efficiency matching the higher rpm (therefore closer to max Hp range).

About REAL rpm limits, this is hard to tell without knowing exact strenght of OEM conrods. What would be safe whithout knowing the numbers would be not to exceed OEM rpm. So if REAL redline rpm (not dash indication) of our engines is 7000 (but I don't know for sure. Paul and Mihnea might tell us exactly on what rpm our ECUs redline is setted) then I would stay with it.
Advantage of having custom conrods made is you choose torque, power and rpm limits, and they make them to your specs (no way I could have any manufacturer tell me theyr conrods exact strenght).


Marco

[diesel des]

Ok, thanks for your help so far. I am inclined to go with the cheeper RR/3B engine and then use the coilpacks and cam cover from a ABY to kill any problems with the spark. As long as i limit torque and therfore BMEP i should be safe. The cash saved on the RR over the ABY would be usfull for injectors/intercooler etc.

So questions i still need answers to are:

1.Are RR rods softer than ABY rods?
2.What is the failure mechinisim of the rods? Bending?
3.What is the maximum safe RPM of the stock 20VT. The Hydrolic tappets are limited to about 7500, yes?
4.What cams would you use to keep torque limited to about 400 ft/lb 550n/m at peak and say 450-500n/m at 7000rpm?
5.Would the head need ported and or big valves to support this?
6.Would ARP/Raceware studs help hold the rods together at high rpm, eg 7000+?

Thanks all for your help!

[Pisobiker]

Des i can try to give an answer to some of those questions:

2) Conrods load is the resultant of inertial loads (which is itself the resultant of the sinusoidal load given by the rotating crankshaft + load of the sinusoidal contribution of conrod big end movement) + combustion forces.
Combustion forces compress conrod, therefore most common failure for over-torqueing a conrod is bending;
Max inertial loads will apply at TDC between the end of scavenging and beginning of intake (thus each 2 crankshaft turns). This loads "stretch" conrods so most common failure is broken conrods.

The latter is usually also the result of fatigue failures (which are still connected with too high speeds, anyway), and it usually causes a lot more damage than when bending (conrods that break through the block, for example).

3) (...part of it) There is someone claiming to have driven succesfully a 500 hp setup with hydraulic lifters at 8000 rpm for a while witout problems.....

4 and 5) Any increase in VE such as higher lift cams, head polishing and porting, bigger valves, will help on running high outputs at lower boost levels.
At resonable power outputs (I think even up to 450 and more hp) it isn't actually absolutely needed, having the supercharging device driving in more air (given the higher temp flow can be cooled properly before entering the cylinder).
In practical terms at same output level, any VE increase will allow lowering boost more than proportionally to VE increase because less boost also means cooler flow therefore more density of charge.
Another advantage could be the possibility of using turbochargers not having extremely high compression ratios, which usually have wider flow ranges therefore giving spool up lower in the rpm.

6) Of course inertial loads will also involve big end bolts or studs. Should be seen which of the two (conrod stem or big end studs) will fail first.



Marco