Future-proofing the AJP

[spitfire4v8]

Jhonno said:

I believe a 410bhp 4.2 exists also.

clive ford's ajp engined griffith was a 4.2 and made 410hp or thereabouts

[Jhonno]

spitfire4v8 said:

Jhonno said:

I believe a 410bhp 4.2 exists also.

clive ford's ajp engined griffith was a 4.2 and made 410hp or thereabouts

That's the one I was thinking of.

[Olivera]

gruffalo said:

The 16V heads may make the car more driveable but I don't see huge power advantages from them.

Basic geometry means that 2 inlet valves and 2 exhaust valves flow better than 1 of each, so I'd expect at least a decent increase in power at high rpm.

Hence I've always been baffled why the Speed 6 doesn't easily outperform the AJP8 for the same capacity, but I've read on PH previously that the Speed 6 cylinder head was originally designed for a capacity of just 3 litres, so therefore can't take advantage of the improved flow of 4 valves per cylinder.

[spitfire4v8]

Olivera said:

Basic geometry means that 2 inlet valves and 2 exhaust valves flow better than 1 of each, so I'd expect at least a decent increase in power at high rpm.

Hence I've always been baffled why the Speed 6 doesn't easily outperform the AJP8 for the same capacity, but I've read on PH previously that the Speed 6 cylinder head was originally designed for a capacity of just 3 litres, so therefore can't take advantage of the improved flow of 4 valves per cylinder.

I too have been baffled by the relative pack of power from the sp6 engines .. the ports are big enough but even in race trim it didn't deliver much power (a couple of slightly larger than 4 litre engines I know of, running without restrictors, have barely managed over 440hp.) You'd have thought 600hp would have been on the cars for a full race sp6 surely ?? the ferarri 458 Speciale is supposed to have 133 hp/liter and that's a road engine. It probably has trick cam timing and intakes etc but come on .. even most good sp6 engines are a good 40-50 shy of that.

[ukkid35]

spitfire4v8 said:

the ferarri 458 Speciale is supposed to have 133 hp/liter and that's a road engine. It probably has trick cam timing and intakes etc but come on .. even most good sp6 engines are a good 40-50 shy of that.

in all fairness I doubt the SP6 development budget would make any impression on the 458 engine's budget

It's worth bearing in mind that the 458 was used for the Ferrari Challenge, and the tyre cost for a season was more than a Str8Six Cerb costs now

[spitfire4v8]

ukkid35 said:

spitfire4v8 said:

the ferarri 458 Speciale is supposed to have 133 hp/liter and that's a road engine. It probably has trick cam timing and intakes etc but come on .. even most good sp6 engines are a good 40-50 shy of that.

in all fairness I doubt the SP6 development budget would make any impression on the 458 engine's budget

It's worth bearing in mind that the 458 was used for the Ferrari Challenge, and the tyre cost for a season was more than a Str8Six Cerb costs now

agreed on the budget, but the point remains that the sp6 seems to flatly refuse to give a good specific power output even in race trim, but the fezza can do it in road trim. Even allowing for mega budgets that's a difficult one to understand. Hp is airflow, engine designers have pretty much understood since the dawn of performance development what it takes to shift air.

[m4tti]

spitfire4v8 said:

the ferarri 458 Speciale is supposed to have 133 hp/liter and that's a road engine. It probably has trick cam timing and intakes etc but come on .. even most good sp6 engines are a good 40-50 shy of that.

Flat plane crank, light weight components/low reciprocating mass, DLC coatings, direct injection, vvt, optimised intake and exhaust config, and revs reliably to 9k rpm.

When you put that lot together it’s going to be pretty special.

A Honda S2000 is probably a closer comparison.

[AW111]

Byker28i said:

Jhonno said:

AW111 said:

Byker28i said:

but are the current heads so compromised that there's another 30% of power available with new heads? Is that possible?

I can only see major power gains if there's a breathing problem at high RPM.

How quickly does the (stock) torque drop off at the top end?

Someone pls post a dyno graph.

Power does tend to tail off over 6-6.5k

But is there 30% to be gained? It seems rather a lot
"but you would have over 500bhp ,a 4.2 with 460bhp." seeing as a good standard 4.2 from the factory was 340bhp


This is mine, ACT manifolds and exhaust, mapped and some other magic

From that graph, torque @ peak power (7,000 RPM) is about 275 lb.ft

To raise that by 30% would require raising that torque value to 357 lb.ft - which is higher than the current peak torque of around 325 lb.ft

So I can't see a 30% gain being possible on your engine @ 7000 RPM. Maybe if you also revved it higher, but 30% is a lot.


For comparison, my 1998 JDM 1600 makes just on 160 hp, but that's at 7,800 rpm, with ITB's and 5 valves/cyl.

The Honda K series' with over 100 bhp/litre also spin to over 8,000 rpm to deliver that power, and I believe the Ferrari mentioned is similar.











Off - topic : It's nice to see software I wrote 20+ years ago still in use


It was 22 degrees, 65% rh and 100 kPa air pressure when the car was run (13/8/2011), and it was accelerating at 15 kph/sec.
Total drive line inertia : 4.017 kg.m
Flywheel power correction mode : shoot_8

[Byker28i]

Jhonno said:

I doubt the 30%, but.. Even an old A-Series/Pinto can make 100bhp/L..
There is power to be had out of the head. Imo.
I believe a 410bhp 4.2 exists also, and my 4.5 makes 430bhp.

spitfire4v8 said:

clive ford's ajp engined griffith was a 4.2 and made 410hp or thereabouts

Anything special about that 4.2?
Is that a true 4.2 or a 4.5? I know a friend with a late 4.2 (4.5 bottom end) that your mapping makes 380, without any of your other work mines had...

Edited by Byker28i on Tuesday 15th June 07:22

[Byker28i]

AW111 said:

Byker28i said:

Jhonno said:

AW111 said:

Byker28i said:

but are the current heads so compromised that there's another 30% of power available with new heads? Is that possible?

I can only see major power gains if there's a breathing problem at high RPM.

How quickly does the (stock) torque drop off at the top end?

Someone pls post a dyno graph.

Power does tend to tail off over 6-6.5k

But is there 30% to be gained? It seems rather a lot
"but you would have over 500bhp ,a 4.2 with 460bhp." seeing as a good standard 4.2 from the factory was 340bhp


This is mine, ACT manifolds and exhaust, mapped and some other magic

From that graph, torque @ peak power (7,000 RPM) is about 275 lb.ft

To raise that by 30% would require raising that torque value to 357 lb.ft - which is higher than the current peak torque of around 325 lb.ft

So I can't see a 30% gain being possible on your engine @ 7000 RPM. Maybe if you also revved it higher, but 30% is a lot.


For comparison, my 1998 JDM 1600 makes just on 160 hp, but that's at 7,800 rpm, with ITB's and 5 valves/cyl.

The Honda K series' with over 100 bhp/litre also spin to over 8,000 rpm to deliver that power, and I believe the Ferrari mentioned is similar.











Off - topic : It's nice to see software I wrote 20+ years ago still in use


It was 22 degrees, 65% rh and 100 kPa air pressure when the car was run (13/8/2011), and it was accelerating at 15 kph/sec.
Total drive line inertia : 4.017 kg.m
Flywheel power correction mode : shoot_8

From 2019 SRR day after the engine rebuild



Best comment from friends after that day when showing the results from everyone was "Only in the TVR world could your 370bhp be considered underpowered"

[spitfire4v8]

Byker28i said:

Jhonno said:

I doubt the 30%, but.. Even an old A-Series/Pinto can make 100bhp/L..
There is power to be had out of the head. Imo.
I believe a 410bhp 4.2 exists also, and my 4.5 makes 430bhp.

spitfire4v8 said:

clive ford's ajp engined griffith was a 4.2 and made 410hp or thereabouts

Anything special about that 4.2?
Is that a true 4.2 or a 4.5? I know a friend with a late 4.2 (4.5 bottom end) that your mapping makes 380, without any of your other work mines had...

Edited by Byker28i on Tuesday 15th June 07:22

It was definitely a 4.2 .. clive did some home head porting and fitted some lovely exhaust manifolds. I mapped it on the emerald ecu. It popped up at an open day a couple of years later in 2010 and made 404hp so wasn't a fluke

[Byker28i]

I know when you mapped mine it was 360 and had cracked manifolds, so replaced them with the ACT tuned length, some new coils and leads and that made the 380.

Interesting to see theres more possible, so maybe heads could be the difference if people were chasing figures? A 4.7 with different heads?

[rev-erend]

Perhaps people should be chasing reliability and longevity rather than more power



Have a few owners put an Chevy LS instead. Guess that can increase the BHP.

[Jhonno]

rev-erend said:

Perhaps people should be chasing reliability and longevity rather than more power



Have a few owners put an Chevy LS instead. Guess that can increase the BHP.

That would be making the assumption nothing was updated/renewed/made in a better material as part of the process..

This is also hardly BHP chasing, it is rebuilds with a bit of headwork effectively.

A stock LS3 has more torque, any LS has massive tuning potential.. But no need to open the LS can of worms and we aren't chasing power anyway..

Edited by Jhonno on Tuesday 15th June 11:10

[gruffalo]

rev-erend said:

Perhaps people should be chasing reliability and longevity rather than more power



Have a few owners put an Chevy LS instead. Guess that can increase the BHP.

I have to say the AJP is not unreliable, it does like regular maintenance but in 13 years of ownership the engine has never let me down.

[Byker28i]

gruffalo said:

I have to say the AJP is not unreliable, it does like regular maintenance but in 13 years of ownership the engine has never let me down.

mine only wore the valve guides, but then it's only got just over 60K miles

[rev-erend]

Sorry for the LS3 can of worms but guess it's a real option years in the future if crucial parts
cannot be obtained but we will all probably be driving nuclear powered cars by then or only allowed to
see cars like this in a museum.

[AW111]

Looking at those graphs again, there does appear to be some potential there, if not 30% - the torque peak is quite high in the rev range (5,500 or so), but it tails off quite quickly.

If the breathing could be improved by better port shaping, you'd need cams to match.

[Jhonno]

AW111 said:

Looking at those graphs again, there does appear to be some potential there, if not 30% - the torque peak is quite high in the rev range (5,500 or so), but it tails off quite quickly.

If the breathing could be improved by better port shaping, you'd need cams to match.

Mine has an odd torque curve..

It is flat from 2.9-4.8k (~345lbft), then jumps 30lbft and stays there until 6k, where it quickly tails off..

My exhaust is/was too small though.. 2" decats, 2.1" rear section. Need to get a proper one made up. Wonder if that is the cause.

[AW111]

Jhonno said:

Mine has an odd torque curve..

It is flat from 2.9-4.8k (~345lbft), then jumps 30lbft and stays there until 6k, where it quickly tails off..

My exhaust is/was too small though.. 2" decats, 2.1" rear section. Need to get a proper one made up. Wonder if that is the cause.

That does seem odd.

I know nothing about the TVR engine except what I've read, but for comparison I'm running a single 2 1/4" exhaust & cat for my 160 HP 1.6 litre.

2 x 2" does seem a bit small for a 4.x litre.

ps
Why decat? Extensive reading indicated that a suitable sized cat has f-all effect on power.