Highest torque / cid ?

[tapsak4]

What are the highest torque number per cubic inch you've seen on a n/a Rover V8? I'm after true numbers from an engine dyno - not anything on rollers..... If I understand correctly, torque numbers from rollers are neither very easy to compare.... nor repeatable on different dynos.

What are the critical issues limiting this (VE, thermal and mechanical efficiency)? How does it respond to changes in bore diameter, stroke, rod ratio, usable rev range, cylinder head restraints, intake and exhaus design, comp ratio, etc ?

I trust the stock numbers are well below 1. In the US magazines figures toward 1.25 and 1.35 can be found for GM engines with Vortec heads and Gen III engines repectively (mos tested w/o any auxilliaries) and also for other well thought-out combinations.

Br,

Tapani

[HairbearTE]

It is possible to make 350lbs with a 5 liter rover so that puts it straight into 1.18-1.2 ish at least. I am sure that racing engines using the Wildcat cylinder head will have surpassed this and there are dyno graphs on the Wildcat website I believe. The valve layout in the standard rover head is not ideal and will never allow it to compare favourably with great designs like the L92 genIII for example. Another thing to consider is that if you have two engines of basic similar design, say two pushrod v8's for example, the smaller capicity of the two is likely to make less TQ/Cui because losses through friction within the engine will be smaller as a percentage of total output on the larger capacity engine. Obviusly this dosen't favour the Rover engine in these kind of comparisons.

[kiwicar]

Sorry to say this but it isn't quite as simple as "building for maximum torque" because you don't end up with what you might expect.
The design for true maximum torque would be to go for highest V/E ie cylinder filling with the largest practical piston diamiter (max pressure over greatest area). this would mean an engine that made maximum use of shockwave tuning of the inlet and especially the exhaust tracts and lots of overlap on the cam to give you a VE over 1. I am afraid you would not be putting it in your Range rover as peak torque would be around 5500 to 6000revs on an engine like the 327 chevy (reconned to be the most V/E eficiant ) and would be a right dog off idle.
For Max usable torque at low revs and a good spread of torque with some ability to rev, assuming petrol, I would go for bore to stroke about square 9.75 to 10 to 1 CR on ally heads, a short period high lift cam (mechanical roller preferably) with a wide LSA, good free flowing heads as cast, definatly not ported out standard heads, valves that are minimally shrouded by the bores. A long inlet tract fuel injection set up with long small bore exhaust headers and the whole lot built out of the lightest parts I could buy.
I could give a spec for a chevy if you want but others would be better for the rover.
It all seems a bit bench racing to me though, as really all you need to do for torque is to go for a bigger displacment.... I think Rosco's solution is the best I have heard of in a long long time .
Or just build a turbo engine and keep the compression reasonably high and inter-cool and water inject to avoid detonation.
Best of luck
Mike

[kiwicar]

Or as Hearbear says buy an L92 gen III with the truck heads and inlet manifold.
Mike

[tapsak4]

Great answers, thanks

I'm not asking this to do an engine for the Range Rover.... just to compare different basic designs in this respect.

Keep the answers coming with real life examples (numbers from from engines of different status) - let's see what we get !



Tapani

[kiwicar]

Ok I was at one point thinking of putting a small block Chevy in a 101FC landrover, the engine spec based of cheep parts available off ebay and aiming for a wide spread of power low down was as follows.
Two piece real seal block
3.875" crank (cast iron internal ballanced)
6" rods I beam rods
+40 JE reverse crown hyper thingy pistons (forgotton what the deck height works out at).
cam spec, comp cams online catalogue is down at the moment so I can't find the number but the spec was roughly hydraulic roller cam 218deg at .05" inlet, 224deg at .05 exhaust with at least .520 lift on 1.5 ratio rockers and 114 deg LSA small base circle.
1.6 ratio rockers
AFR street 195 heads (the competition ones ones were over budget) however having bought the RHS 235cc heads I would now go for their 200cc heads.
belt drive cam drive
long tube headers with ballance pipe
The chevy tunnel port efi manifold matched to the heads with megasquirt EFI controler.
All on a T56 box into an adapted RR transfer case.
hope this isn't too boaring
Best regards
Mike

[dnb]

I managed 350 ftlbs @ 4000ish rpm in my Griff. (dyno graph is in the dyno section) We did 15 runs over the course of a morning and peak torque was always the within a percent or so.

In round numbers, torque per CI is a mere 1.14

The engine spec is:

5 litre Rover v8
tweaked (big valve) TVR heads
10.7:1 CR (estimated)
H404 cam
one-off twin plenum inlet with long primaries

[ChrisJC]

That's on a rolling road though isn't it? (rather than an engine dyno)

Chris.

[5000SE]

If I understand correctly, torque numbers from rollers are neither very easy to compare.... nor repeatable on different dynos.

I don't see why - as long as it's a reputable dyno being run by a good operator and he enters the correct air temp and pressure. If it's on a known type of car, the etsimates for transmission loss should be pretty accurate.
If the hp is right, the torque has to be - they're only separated by a simple sum after all.

I had a 4.6 with stage 3 big valve heads and a Hybrid 200 cam, but slightly trick in that it was running twin plenum with two flapper-type airflowmeters. It made 367lbft at around 3700rpm on the rollers at Power Engineering. I think at the time it was the torquiest results V8 Dev had from one of their builds.

[topsparks]

My V8D 5.5 made 370 bhp and 430 ftlb of torque!,fitted with a 404 mechanical cam,Rob reworked my standard 500 heads,GroupA rockers ,Emerald ecu and ACT triple plenum.
Griff was as quick as an LS6 powered Chim!