Cats, MOTs and power - ACT content

[spitfire4v8]

Have a griffith in at the moment .. the car has an Emerald K3 ecu and the ACT long exhaust manifolds and previously had the decat pipes fitted. Current owner has fitted the corresponding act cats and I've just fitted a wideband lambda and mapped it all up.

All relatively common stuff so far.

What's interesting though is that this car has made 350hp / 350lb.ft

I don't know what cam is fitted - the power is bordering stealth / h404 territory , but what i wanted to say is that anyone who is using the ACT manifolds should not worry about refitting catalysts for MOT time or indeed running cats all the time, they are very free flowing going by what this car has made. Unless you are really chasing power in the upper 300s / close to 400hp there really is no problem running cats such as these.

graph :

[motul1974]

That's good to hear. Mark Adams said the same thing about them to me as I've fitted cats to my SLOWLY getting together GEMS rebuild.

[KKson]

Blimey, that's impressive power output and very linear. Presumably a 5l Griff?

I do need to get my 450 SEAC back on a RR. Mark Adams gave it a health check last year after I'd recommissioned it, having spent 15 years in storage, and it's running a bog standard 3.5 EFi ECU. Power was still almost 280bhp and 353lb.ft. I've now got my hands on an adjustable ECU off an ex-racing Vitesse, which supposedly put out 350bhp, so keen to bolt it in and get it adjusted. Engine is also running adjustable solid lifters.

[spitfire4v8]

Yes a 5litre, no idea on if it's had any other work other than the manifolds and emerald ecu .. it's excellent power though and a very good indication that the cats are not robbing much power

[Classic Chim]

spitfire4v8 said:

Yes a 5litre, no idea on if it's had any other work other than the manifolds and emerald ecu .. it's excellent power though and a very good indication that the cats are not robbing much power

How would it produce that power if it was standard on a worn lump, genuine question.
I assume this has different injectors and port matched stage 3/4 heads etc or all the money people have been spending for years with any number of builders was a waste of time
Must be rebuilt surely.
Be nice to get some engine specs as that’s one hell of a motor going by that graph.

[Englishman]

Certainly impressive

My standard (except for ACT induction hoses) Griff 500 made 300hp / 330lb.ft at Surrey Rolling Road a couple of years ago, I wonder what that would make either without any or with ACT catalytic converters?

[spitfire4v8]

Classic Chim said:

How would it produce that power if it was standard on a worn lump, genuine question.
I assume this has different injectors and port matched stage 3/4 heads etc or all the money people have been spending for years with any number of builders was a waste of time
Must be rebuilt surely.
Be nice to get some engine specs as that’s one hell of a motor going by that graph.

It's got a stealth cam in it .. just spoke to the owner .. otherwise engine is untouched.

I know people and some engine builders poopoo the std tvr 5litre heads, but almost all the very high hp engines i've seen have used these heads. My own v8S made 355hp on std tvr 5 litre heads. My Tuscan racer has tvr 5litre heads (it's actually based on a tvr 5 litre engine) and makes just shy of 400hp!
the tvr 5 litre heads are (in my experience) excellent.

[Classic Chim]

It must have excellent compression and indeed a high lift cam as others with more mods on 5.0 engine barely makes 325. Maybe the cats are keeping some back pressure in the game in a good way.
By removing the main cat you gain 10 hp but loose a touch of grunt on my 450 so those exhausts might offer 15 or more on a good 5.0 maybe.
The flow is so much better for sure.

[Podie]

Blimey - very healthy numbers! Anything more to be had from a blended trumpet base?

Long time no see Joo hope you're well.

[spitfire4v8]

Hi Pod .. well you'd hope it would add another 10hp as that's what i typically see.
Best 5 litre I've had in a road car is pasco's griffith .. that made 370hp so the possibility is certainly there.