2.4 Inlet General 2.4 Inlet Manifold Questions

you need a 2.4 inlet manifold (they do come up for sale every now and again) or import one from the usa - don't forget the oil breather gasket

you also require an alternator suppressor, a universal type is perfect

you will need some servo piping and possibly the servo one way valve
I've been following this thread long time ago, then lost the point and now picked up again somewhere in the middle.

I fitted a 2.4 intake mani to my astra last year and I'm quite happy with the power output (almost 170 ponies now) but you all know what I mean when I say you get used to it way to fast. :roll:
Now I'm looking for another possibility to gain some extra horses.

My setup so far:
intake side:
2.4 intake mani - stock TB - stock intake piping - K&n panel filter - vectra C final tube to grille (bigger diameter)
exhaust side:
dbilas 4 : 1 exhaust header - precat drilled out - stock cat - 65mm catback with "almost no" middle silencer and 2x "Japan style" muffler
NO EGR crap at all
stock cams

I was thinking about doing the FPR mod and improve intake side a little more by using the vectra C pipe from TB to air filter (instead of the crappy oval original one)
then maybe replace original filter box by the dbilas system.

What about TB improvements? Are these 2.4 / 2.0 TB issues sorted out?
Do 2.0 SC injectors make sense in my config already?
Is a sports cat really necessary (the car is loud enough already) 63..
Where can I get cheap cams (not too aggressive, I still want to be able to pass German exhaust tests) and do I necessarily need stronger valve springs with other cams?

ECU still needs to be remapped but as I'm thinking about improving some parts again I'll of course want that done afterwards.

I know that's lots of questions but if somebody could take the time to answer as many as possible it would also be a good summary for every newcomer in this thread

Thanks in advance - really appreciate your help!
170 seems a bit high with your setup. ( No offense)

Your best option is to get the TB ported, the 2.4TB has not been sorted as of yet. Then better intake pipe, MIkeS is selling one at the moment.

As for Cams either Piper regrings / some times DB items turn up or you can get the Comp Cams or if funds are open schrick items.

The a RE-MAP.

Unless you are going above 200bhp then you will not really need the bigger injectors.
Thanks for your reply Sjdickso,
In fact, I don't care about numbers at all. So I'm not mad at you cheers.. All I know is that the dyno run at Hitec in Germany resulted in 123,9 kW after the listed mods. I don't have measurement of the car being stock so nothing to compare unfortunately.

Thanks for the advice to further improve the intake side. That also fits my intention to spend little money in effective tuning.
I'll see if I can find a company doing TB porting (doubt I can do that myself even without having 2 left feet I'm a total noob when it comes to metal treatment)
I've also read somewhere to turn the TB so it opens with the air flow. Does that make sense at all? Is it easy to do that, I mean is it simply turn and bolt on?
Regarding the intake pipe I'll go for the Vectra C pipe (like the original look) it's round instead of the original oval pipe and has a nice 90° bend without being a bottleneck right above the TB.
Only issue is that there's no possibility to connect the FPR hose, that's why I thought about doing the FPR mod with new one way valve and seperate connector or drill a whole into the intake and glue the connector in there.
Also unsure whicht air filter to take.
Anyone got experience with the dbilas system? Pic source is Regal Autosport Cause I thought going for the Z16LET Airbox Pic source is SH Fahrzeugtechnikmight improve airflow and still leave the original stock look.

As for cams, I'd like to stay cheap but reliable (I know it's an original thought) but more important not too aggressive so I assume Piper regrind is the #1 choice? Do they ship to Germay? Do I need to replace Valve springs?

OK no injectors needed < 200 bhp

What about the cat? Just want to make sure further improvement of intake side makes sense even with stock cat!?


Former Staff
Senior Member
I am extremely suprised that you're engine is producing that kind of power with the mods that you have listed. I would like to see your dyno graph. The 2.4 inlet has been notorious for reducing torque power and showing very little gain in bhp.
JohnnyN said:
I am extremely suprised that you're engine is producing that kind of power with the mods that you have listed. I would like to see your dyno graph. The 2.4 inlet has been notorious for reducing torque power and showing very little gain in bhp.
There you are Bro' (date is wrong it was in April 2008)

As you can see on top this was done at Hitec's dyno in Viernheim / Germany (they should be well known here for their SC conversions - afaik they even cooperate with Courtenay)
and peak power was reached when hitting the rev limiter, so probably changing the limiter to 7000rpm will already do the trick for some extra ponies but Hitec couldn't do that to the Astra's ECU (they seemed to be familiar with the speedster ECU only)

But again, I really don't care about all those numbers ... (All I want is moooooooore power) showo.. :mrgreen:

So to summarize the suggestions related to my config:
- further improvement on intake (vectra c or custom pipe from TB to air filter / port TB / maybe get 'better' filter like dbilas flowmaster)
- further improvement on exhaust system by changing the stock cat with a 200 cell sports cat (will probably make the car too loud so this will be well considered)
- more important: change cams (dbials / schrick or Kreis cams are too expensive so reground piper cams are #1 choice) and together with that do the chain kit (car has run 100.000 km already so I gues it doesn't harm to do the kit with cams together)

and most important: get custom mapping! But unfortunately that seems to be a pretty tough task. I'm not aware of anyone in Germany with a setup like mine (when cams are done) so there seems to be no experience at all. I'm aware of one guy having done a mapping with 2.4 intake and dbilas exhaust and the result was smoothed power and torque lines and 1 extra bhp compared to stock mapping. :LOL:
Another guy who had his speedster (also 2.4 intake and lexmaul exhaust header with sports cat) mapped almost got the engine melted by famous german tuner with 3 letters (name not to be announced in public)
so where the hell to find a trustworthy person with skills do to a good custom mapping regarding all these mods :?:
Thanks guys, I'll try to go for Piper cams then and have Klasen do a custom mapping afterwards.
Where do I find the specs of Piper cams?

I found this on the piper website. Are those the specs for regrinding? How long do they usually need to do that and send the cams back?


If you read the description

This manifold was a take off from a brand new never fired 2.2 Ecotec
then I would take it that this is the standard 2.2 inlet manifold, but they are simply stating that it will fit either the 2.2 or the 2.4
dont worry about the 200 cell sports cat, noise doesn't matter too much where i live and to be honest it sounds nicer, but i was secretly dissapointed at how quite it still is.(my mates evo still drowns me out)