11 replies to this topic

[Mk3vr6/24v]

Hi just a quick question for the z20let folk
Has any one of you lot messed about with a xev inlet with the flaps inside?
Im after some more low end torque off boost
Little back ground
The engine is Standard as far as I know,I totally forgot to check under the pistons but from above look same as leh pistons. I did the head gasket and used the head of the leh engine Ive got to save time waiting for machine shop
Multi angle valve seats and cleaned up exhaust ports, standard turbo
Ive deglazed the bores,not burning hardly any oil now if any as the dip stick reading not changed and using shell 5w30
At the min Im doing all the brake pipes and bushes and suspension so the Zafira is off road and got a little time to mess with the manifold




Omg its been a right ball ache to get this far

[Nev]

My bet is that the XEV inlet manifold is already tuned for good low end torque. Maybe you could narrow the tubes or some such, but I think you'd be likely to cause more problems than cure them. You probably know this already, but to increase low end torque the general principle is to narrow the tubes to increase flow speed, however doing this in practice is hard to do.

 

BTW, the Z20LET inlet port form factor is very similar (maybe identical) to the XEV, so you could try installing/looking at a Z20LET inlet manifold instead as the Z20LET "might" be tuned for more pre-turbo spool torque.

 

GL, sounds interesting.

Edited by Nev, 14 November 2017 - 07:38 AM.

[ayresyy]

 I guess the 'theory' of the XEV inlet is correct. Long runners for low RPM then the flap opens at higher RPM and shortens the runners. It is vacuum operated though so that could be an issue for a boosted engine. You would also need a way of operating the control valve at the correct RPM. I do suspect the XEV manifold is tuned more for N/A induction rather than forced induction, but as far as I know it's not been tried. The inlet ports do match so who knows?

Edited by ayresyy, 14 November 2017 - 07:57 AM.

[Mk3vr6/24v]

Cheers for the replies chaps Thats the top half of the manifold Ive not got round to the other bit yet Ive got two well will try 2 options 1, is use two one way valves, first one on the inlet vacuum so with engine started the vac will Close the butterflies making the inlet trac length long and keep them closed with part throttle and the second one way valve from the turbo and maybe a adjustable restrictor So the boost will open the butterflies in the manifold If that makes sense to you all 2 is to use the solenoid on the inlet, activated with the pressure switch from the water injection I can only see it causing a drop in power on the top end but I dont really go up there unless I break traction in the rain

[Mk3vr6/24v]

Well tried to fit the inlet, the lower part of the inlet catches the oil cooler! Its about 15mm away to sit flush grrrrr Rough measurements comparing the let inlet and xev With the flaps open runners are approx 3inchs shorter With the flaps closed runners are Couple of inches short of twice the standard let length Got pictures to put up later but the ports on the XEV are a fraction larger than the LET Compared using an elring inlet manifold gasket which sits perfectly on the XEV where as on the LET You can see the gasket is slightly larger than the inlet ports <1mm Need to move the oil cooler now

[Nev]

I'd be a little wary of using the inlet gasket as proof of inlet port size/location, the genuine OEM one I used in the past was poorly sized and needed trimming.

 

Probably better to use an engineer's pen or some putty and match them up to see the witness marks.

Edited by Nev, 01 December 2017 - 11:32 AM.

[Mk3vr6/24v]

I was just comparing the differences with the same gasket hole, just to quickly visually see
The normal inlet is back on now to get the mot out of the way
Bit gutted
Zoom in on the LET manifold to see the slight difference

[Nev]

I was just comparing the differences with the same gasket hole, just to quickly visually see
The normal inlet is back on now to get the mot out of the way
Bit gutted
Zoom in on the LET manifold to see the slight difference

 

TBH, that gasket looks pretty spot on, I think I may have had issues with mine as I was installing a rather badly cast 3rd party inlet manifold.

 

Don't despair, at least you had a go at doing something insightful that took some gumption, which is more than many people, who seem to be preoccupied with mundane things like polishing and painting unnecessary bits of their car. Loads of R&D ends in failure, but by failing you are learning something in the process (and contributing to the public knowledge base by publishing it).

 

Will you revisit the project after the MOT?

 

At one point I was considering designing an inlet manifold with extendable runners (using 4 lengths of silicone pipes and some tapered metal runners) to find the sweet spot. But in the end, without lots of easily available dyno time I just bought a 3rd party jobby as I already had enough to do in my project.

 

 

 

Edited by Nev, 02 December 2017 - 09:49 AM.

[Mk3vr6/24v]

Well thank you very much, The old gasket I took off was slightly smaller than the LET inlet manifold The elring one Im using now sits near enough perfect(I trimmed No4 ) Ive got a vxr engine sat in house to see exactly where it is catching but my back is a bit delicate with driving a KA!!! Ive got a good feeling about this manifold, On the N/A x20xev the folk swap to the LET inlet manifold to gain 5-9bhp up top end for the loss of low mid range, Yes most definitely be attempting this, the idea of variable lengths inlet with a actuator to shorten the runners with boost be good if I had the fabrication tools(dont have the skills but can learn lol)

[Madmitch]

Just a thought, probably off target but maybe relevant.  My everyday wheels are a BMW530d Touring.  The engine came as standard with swirl flap valves in a fixed length inlet tract which BMW say is to improve atomising of the fuel at low engine speeds, the flaps turn as the revs rise but have no effect on the length of the inlet tract.  Unfortunately they have a reputation for breaking off and wrecking the engine so I removed mine years ago, a friend with an X3 removed his too.  When hot you cannot tell any difference between before and after and it sails through it's MOT without any problems, there is an almost imperceptible flat spot for the first couple of minutes from cold but it's gone by the time I get to the end of our lane.  I know shortening both inlet and exhaust systems moves maximum power and torque up the rev range but I'm much happier to do without the risks that come with BMW's version of swirl flaps!

[Arno]

Swirl flaps are usually a diesel (and perhaps direct injection petrol) thing to get enough air movement/turbulence in the combustion chamber to aid in a good combustion at lower loads and rpm's. Not sure it would do much in a port-injected petrol engine.

 

Having said that.. Vauxhall/Opel use a similar flap/valve system on nome of their smaller petrol engines with the twin-port setup and port injection:

 

 

It's based on a cylinder head that 'exposes' both separate intake ports of each cylinder in the head and then adds a ECU controlled flap in one of the ports on each cylinder.

 

This allows it to shut off (most) of one intake port on each cylinder at low/mid load to increase the air velocity in the remaining open port and help fuel atomisation and efficiency.

 

Other manufacturers like Honda and Toyota do similar things with their variable valve setups on the 'eco' engines by running a 16V engine as a 12V under lower load and keeping 1 intake valve in each cylinder closed.

 

Bye, Arno.

[Nev]

The old Corvette LT5 engine had a twin inlet port system that could shut down, developed by Lotus in the later 80s and early 90s.

 

Edited by Nev, 05 December 2017 - 09:20 AM.