57 replies to this topic

[Steffe]

To Winstar: You recommend removing the cone shaped barrel at the outlet of the airbox. What purpose do that part have? It seems to be a sort of restrictor or something.

[Steve B]

Has anyone got an illustrated guide to modification of the standard box? It doesn't make it too loud does it?

[Paulus H]

A better question would be, has anyone got pictures of the std intake system? If it were not for the late hour, I would go into the attic and photograph my old intake system. Vauxhall have quite a good reputation for inlet/airboxes but I really don't see how this system can work efficiently. As an ex-auto engineer (HND in Automotive Design) and once an avid reader of David Vizards work (from 30 years ago), I think DV would be appalled by the VX design. I remember quite clearly many of the DV principles. I don't remember any of DV's drawings resembling anything like the std VX design. Anyway, back to my first sentence. Looking at the convoluted and contorted path of the inlet charge of the std NA intake system I cannot see how it can be efficient. Thinking as an engineer, throwing a big diameter pipe (as in ITG) between the filter and inlet manifold does not look like the ideal solution either. To me it appears to be the right diameter for flowing enough air for 400 bhp not less than 200. In other words the ITG is TOO large a diameter to work efficiently with the amount of air it has to flow. To charge the cylinders properly the inlet charge needs to be moving quickly, my feeling is that ITG is too large a diameter and therefore the inlet charge will be moving to slowly to achieve good charging of the cylinders. Due to the relatively short inlet manifold, it would appear to me that good speed in the air box would significantly increase cylinder charging... I am not having a go at Winstar, maybe we can agree some common ground...

Edited by Paulus H, 01 March 2010 - 12:59 AM.

[Winstar]

To Winstar:
You recommend removing the cone shaped barrel at the outlet of the airbox.
What purpose do that part have?
It seems to be a sort of restrictor or something.

Yes I have, there is some debate as to whether it forms a tuned length in the inlet and that removing it will cause a loss of torque. It's purpose is that it is a Noise reduction feature as the inlet system is a carry over from a Vectra (I think).

A better question would be, has anyone got pictures of the std intake system?

If it were not for the late hour, I would go into the attic and photograph my old intake system.

Vauxhall have quite a good reputation for inlet/airboxes but I really don't see how this system can work efficiently.

As an ex-auto engineer (HND in Automotive Design) and once an avid reader of David Vizards work (from 30 years ago), I think DV would be appalled by the VX design. I remember quite clearly many of the DV principles. I don't remember any of DV's drawings resembling anything like the std VX design.

As much as DV did some good work as you say it was 30 years ago and the automotive engineering world has moved on a whole lot since then. Once you've removed the NVH cone mensioned above and reduced the length od the inlet pipe to match the VX intake only has one real bad feature ant that is the slight S-bend but in reallity this won't cause much of a loss. Features like the offset inlet and outlet are so that the flow is slowed and evenly distributed as it passes through the filter. The flat pipe and cobra head is to try to get even flow either side of the throttle butterfly.

[Paulus H]

Win. I would be interested to hear your opinion of a "ITG type" inlet but using a smaller diameter pipe between the filter and manifold. Ie charge comes through the filter at low speed and is forced to accelerate to the same speed as the charge speed entering the inlet manifold. Perhaps a slightly conical pipe would work better where charge speed gradually increases as it reaches the inlet manifold? I am NOT yanking your chain, I am genuinely interest in increasing the efficiency of the engine. As to why I ask the question is this, I am still dubious regarding (even a modified version of) the standard inlet system. I am equally unconvinced that induction systems originally aimed at "Corsa-boys" are designed intelligently. Once again a broader question is why does this engine even modified with cams, head mods and ITB's produce such low specific HP?

[Mike (Cliffie)]

I just fitted an ITG today, standard airbox before.

All I can say is, Who the hell stole my VSE during the night?! I only really bought it (2nd hand) because of the noise and am very happy with that

Glad it turned up, pleased you fitted it and chuffed you are happy with it.

[alanoo]

You could work on the inlet pipe as much as you want, this won't help anything with the crappy plenum design, and this is the worst piece on the inlet side

[j0n]

No one has mentioned K&N I dont think, thoughts?

[slindborg]

Once again a broader question is why does this engine even modified with cams, head mods and ITB's produce such low specific HP?

because shes just not a revvy engine Which is traditionally where most of the power comes form when doing these mods.

Not saying they wont add anything lower down the rev range, but their influence is much mroe noticeable top end. and with a 7mile stroke like the Z22, you are fcuked unless you spend a mint like Vocky

[Steve B]

With the talk of servicing I thought mine could probably do with a new air filter (panel in the box), so when fitting it makes sense to do "the air box mods", any pics please?

[Steve B]

Well fitted a K&N panel in the OEM box today, has to have been the most time consuming filter change I've ever done, but anyway. I removed the trumpet in the box and I adjusted how the fabric/wire inlet tube sat. I basically pulled it out so that the tube terminated in the centre of the box rather than the far edge. Will be interesting to see if I can feel any difference at all (even if its just down to the filthy old filter having been replaced).

[oakmere]

Just my 2p worth I tried the larger diameter pipe from the STD airbox to the tb and noticed the drop in lb mid range but no drop was felt with the itg just smooth power delivery though I would not say I could notice any power increase. Cheers Oakmere

[Steve B]

Well drove the car to work today, I found that low down pulling off the car pulled a lot more cleanly, flat spots have gone. It is no different in volume until after 4000rpm where it now sounds deeper. Whole rev range seems smoother in general. Could all just be down to a clean filter, who knows

[Paulus H]

Pictures of std air box....








None of the above bodes well.

When I was running Thorney phase 2 I was very happy with the power delivery. I thought going for the ITG would be an improvement. Then I bought an ITG....



To begin with I kept chasing the red line because the car sounded awesome. At that time I thought the ITG was an improvement.

After a while I realized I was changing gear well before the red line because the power was trailing off early. This never happened prior to fitting the ITG.

With the benefit of hindsight I would say the car felt sportier to drive and had a more liner power delivery with the "strange" std induction system.

The sound was awesome with ITG but it hurt the power curve of the car.

I find it hard to believe but I recommend the strange std induction in preference to the ITG.

My car has additional mods now and has a great power curve as seen below. However I would not recommend the ITG unless you have at least 2.4 manifold....



Best regards, Paul...

Edited by Paulus H, 20 September 2010 - 09:29 PM.

[Winstar]

I'm going to have to comment

Pictures of std air box....


this ribbing will cause very little pressure loss in that locaton and are there to stop the pipe colapsing under vacume.


These ribs are there because the sides of the box would be like a rolf harris wobbel board with the engine vibrations and the air flow should go nowhere near them.


I'll give you the S bend that's inexplicable*, the corrugated section is required to take the (considerable) movement of the engine and the frictional pressure loss down a regular corrugated pattern is low as vortices form in the grooves.

*it was probable designed for another application and just dragged out the parts bin

[Mondo]

I ve been reading this thread with great interest. I have tried a pipercross cone filter, drain pipe etc.. you name it and i have went back to the standard intake system. The only difference I noticed was noise, a loss in mid range torque and small increase in top end. The foam filter also let a lot of crap in that the paper panel keeps out. Didnt take long to come to the conclusion that for normal road use the standard system is best for me as I will never see top end gains that often but the mid range torque I will use. In my humble opinion changing the air intake on a NA will only give noticible gains when coupled with serious engine mods. If I wanted more power it would be the SC route and save faffing around with something that you may or may not notice or even spoil your cars performance somewhat. Cheers

[Paulus H]

I bet no race designer would ever come up with a design like the std VX220 air filter arrangement, however it does appear to work. In all honesty, after initially liking the sporty noise of the ITG I realized it hurt the performance of my car. I now have Chris Tullet 4 branch exhaust manifold, P&P tb and 2.4 inlet manifold - I have retained the ITG. The ITG does seem to work with these mods. However I do not think I would be still using the ITG had these other parts not been fitted.

[styles]

No one has mentioned K&N I dont think, thoughts?

I ran a K&N cone and it wasnt too bad at all. Nice little noise.

I changed to a viper and didnt really notice any difference