M35 Vq25det Runner Spacer

[iamhe77]

So an interesting idea that we saw on the TEPS M35 site before it went down was to install a spacer to slightly increase the length of the runners.

The thought being that it may improve low-mid range torque without sacrificing top end power.

Whilst they installed a 20mm spacer, I went for a 17mm spacer for two reasons:

1. I was concerned to read that the owner had to close his bonnet very carefully due to the increased height and

2. My mate made his V35 plenum spacer from 17mm aluminium, so it was convenient to try with the remains of that sheet (if poor results, little was lost)

First things first was to get a gasket. Unfortunately, the only engines that use this gasket are the vq25det and the vq23de.

Once received, it was then given to have the shape cut, drilled and cleaned up to make the spacer.

Next up, I ripped the intake off from the BOV pipe to the base of the plenum (no pics of dismantling) until this is all I was left with

Next up, install the two extension plates to the existing brackets:

Transmission filler tube (the bright aluminium plate at the back of the engine)

and the fuels pressure regulator bracket (shown with plenum in place)

Next, I needed to get the appropriate length high tensile bolts and studs (settled in grub screws - makes it much easier). Needed to re-drill the holes/slit so they could slide neatly in which was no prob

Screwed the grub screws in where the studs were previously and placed the spacer on the existing gasket which was in excellent condition (pic from passenger side)

Then on goes the gasket and (carefully) the plenum with the three long bolts in the top, the smaller bolt in the lower hole of the plenum and the nuts that were on the original studs screwed onto the two grub screws. All bolts and nuts were tightened to 19nm.

Now just to put it back together again.

Plug the Throttle Body plug in if you have not already done so and screw in the extension brackets (had to push the transmission filler tube ~5mm to the side to line up with the hole. No problem during or since)

Reconnect these 5 hoses to the plenum and the bov pipe to the intercooler pipe and the throttle body.

Then the BOV return pipe

Support bracket and plug in the 2 hoses and 2 plugs

Then put this bracket with the 3 plugs back on. Damn fiddly bolts.

Lastly, I flipped the plastic tube that goes across the front of the engine so that there was less stress on it due to the increase in height.

End result, a noticeably higher sitting plenum, but with plenty of space for the bonnet to close.

Issues!

#1 The 1st issue in the design was that the holes were too small for the bolts with was easily remedied.

#3 Slightly slower to power through the rev range

#2 Fuel economy and idle issues. Once the spacer was installed, both were stuffed. Warm idle was 1000-1100rpm (cold was ~1800rpm!), thus the economy died due to excessive revs when idling and an overly rich mixture when accelerating.

***This was put down to my throttle body. I have since installed another one and my idle is a steady 600rpm when warm and 1000rpm when cold***

Benefits

#1 Increase in torque. Whilst it isn't a massive increase, it is noticeable... especially off boost .

#2 Noticeably cooler engine bay.... I guess due to more space for the air to get in a circulate around the plenum

#3 Hold gear much better now. No more gear change with a slight wiggle on the accelerator when cruising. I light press will have the car increasing speed in 5th... even if you are

in "D"... or course it will still erupt if you stomp on the accelerator

#4 Relevant to anyone else, I dunno... but my car is now like a cop in shit between 3400-4600rpm. Absolute joy in this rev range (quite the surprise initially)

#5 Boost comes on a little earlier.... roughly 200rpm, not much but it is earlier.

#6 Better economy whilst cruising due to no kick-down with little movements of the foot or slight inclines

So all up, pretty happy with it. No real complaints.

The car is a bit more predictable in the way the power comes on and it is a bit nicer on the fuel through the hills and cruising due to holding the higher gears for longer... although still controlled by the right foot. Also nice to have steady (if a bit slow) acceleration off boost. It IS actually usefull in some circumstances

Anyway, just thought I would share.

Edited December 9, 2009 by iamhe77

[66yostagea]

That is well written.

[andy65b]

Nice write up Cam.

Cheers

Andy

[iamhe77]

Thanks guys.

Will look at making up some kits if people are interested.

[southern_tango]

Great job Cam ,it's a really step by step guide...must be in the DIY section

[zei20l]

nice one dude! thanks for the pics and glad the TB worked

one day your old one will be removed from the box it arrived in, for my little project.

anyway, im interested, and my car is pretty much stock, so it will be a good comparison, if only i had enough cash to do a before and after dyno run

[scotty nm35]

nice one dude! thanks for the pics and glad the TB worked

one day your old one will be removed from the box it arrived in, for my little project.

anyway, im interested, and my car is pretty much stock, so it will be a good comparison, if only i had enough cash to do a before and after dyno run

Whats this little project may I ask? I could put that TB to good use you know Iain, are you planning a cable conversion like me?

[scotty nm35]

Nice job Cam, I noticed you cleaned the plenum too, could this be the source of your extra powah?

[Jetwreck]

nice rightup

P.S. it goes 1 - 2 - 3!.....not 1 - 3 - 2!

[iamhe77]

nice one dude! thanks for the pics and glad the TB worked

one day your old one will be removed from the box it arrived in, for my little project.

anyway, im interested, and my car is pretty much stock, so it will be a good comparison, if only i had enough cash to do a before and after dyno run

Yep, many thanks for the TB you sent down Iain. Car is back to being enjoyable to drive again (a lot easier on the gears as well!)

Would have loved to do a before and after dyno. Oh well.

Nice job Cam, I noticed you cleaned the plenum too, could this be the source of your extra powah?

No extra powah... but faster now due to weight saving on all that grime

nice rightup

P.S. it goes 1 - 2 - 3!.....not 1 - 3 - 2!

lol... Just noticed that! Was a bit busy yesterday

[zei20l]

im planning something else at the moment with the TB

[Angus Smart]

Nice, sounds good eh! doesnt look too difficult to do either!

get them made up the same place i got all the flanges cut for the dumps. they were pretty cheap and good lazer cutters!

[mattye]

iamhe77 don't mean to sound like a pesamist but perhaps some before and after dyno sheets before everyone gets too caried away. Although yes u are creating in essence a bigger plenum, ur also making it further for the air to travel. Which is probs why as u said its

#3 Slightly slower to power through the rev range

because having longer runners can make the turbo spool latter.

Just my 2c. I talked to Mercury Garage about runner lengths when i was contemplating geting a front facing plenum a few months ago. They recomended geting a plazmaman rather than a Greddy for this reason because a plazmaman plenum doesn't replace the runners. N with the Greddy because it replaces the runners the turbo was spooling 400 rpm latter than the plazmaman.

PS: as a side note i decided not to get the plenum yet cause i couldn't justify the money YET.

[iamhe77]

iamhe77 don't mean to sound like a pesamist but perhaps some before and after dyno sheets before everyone gets too caried away. Although yes u are creating in essence a bigger plenum, ur also making it further for the air to travel. Which is probs why as u said its because having longer runners can make the turbo spool latter.

Just my 2c. I talked to Mercury Garage about runner lengths when i was contemplating geting a front facing plenum a few months ago. They recomended geting a plazmaman rather than a Greddy for this reason because a plazmaman plenum doesn't replace the runners. N with the Greddy because it replaces the runners the turbo was spooling 400 rpm latter than the plazmaman.

PS: as a side note i decided not to get the plenum yet cause i couldn't justify the money YET.

Thanks for you input Mattye.

Unfortunately I do not have the time nor cash to have before and after dyno runs. I prefer to go by real world test such as

If the car can hold a certain gear on certain inclines on my way to work after the spacer compared to it's inability to do so prior.

If the car can pull up various inclines with changing gears and without accelerator position changes

The difference in the cars ability to drive off boost in different areas

The turbo will not spool later, as more air is getting sucked in, meaning more air is sent through the exhaust manifold which means it would be travelling at a slightly increased velocity and past the exhaust wheel of the turbo, please explain to me how this will cause extra lag? Also please note that in my original post I specifically noted that the turbo spooled 200rpm earlier. This is from experience and not theory.

Also, as stated, it is more a "round out" type of mod which makes the car a bit more comfortable and predictable to drive.

I have not made any power claims whatsoever, nor will I. The "increase in torque" statement comes from 3 sources.

1. ME and my knowledge of MY car in real world circumstances

2. My front axle torque gauge (it certainly is a fair bit more active in the dry now)

3. The fuel leaf screen to make sure that my foot is actually remaing steady during such tests

So my experience flies in the face of what a tuning shop tells you. Maybe if you talk to other tuning workshops their opinion may differ from what you have been told... or it may remain the same.

Regarding your plenum conundrum, would the Greddy unit have shorter runners and the Plazmaman unit retain the stock runner by any chance? This could possibly explain the 400rpm spool difference.

Keep in mind that the design of the plenum is vastly different on an I6 than a V6.

Also note that my car is not like a "cop in shit" but rather a "p_i_g in shit"... ridiculous

Edited December 10, 2009 by iamhe77

[scotty nm35]

I always found longer runners gave more midrange and short were good for the top end, which would mean the turbo spools earlier with a longer runner i guess.

Cam, good on you for custom making a part, and for the results on it I was waiting for. Nice mod.

I was wondering if you can get them cut from some sort of insulating material also, to cut the heat trasfer down?

[Angus Smart]

Scott,

i have seen my friends use some sort of thick vinyl/plastic for the intake on his vw beetle where his custom runners/carby setup meets the heads.

cant see why it couldnt be used here.

[66yostagea]

I always found longer runners gave more midrange and short were good for the top end, which would mean the turbo spools earlier with a longer runner i guess.

Cam, good on you for custom making a part, and for the results on it I was waiting for. Nice mod.

I was wondering if you can get them cut from some sort of insulating material also, to cut the heat trasfer down?

Back in the "carbie" days we used to vary the length of the intakes to adjust for low end torque, long, or max speed, short.

I've just got a Forward Facing Plenum and this topic interests me.

[66yostagea]

I always found longer runners gave more midrange and short were good for the top end, which would mean the turbo spools earlier with a longer runner i guess.

Cam, good on you for custom making a part, and for the results on it I was waiting for. Nice mod.

I was wondering if you can get them cut from some sort of insulating material also, to cut the heat trasfer down?

Back in the "carbie" days we used to vary the length of the intakes to adjust for low end torque, long, or max speed, short.

I've just got a Forward Facing Plenum and this topic interests me.

[SABBAi]

Good stuff there mate. Considered making it in a heat resistant plastic/resin/composite to reduce heat transfer into the plenum???

[iamhe77]

Good stuff there mate. Considered making it in a heat resistant plastic/resin/composite to reduce heat transfer into the plenum???

I had thought about it initially, but I was more concerned with making it up and testing it out.

I still have not checked to see how hot the spacer gets, but I have a couple of long drives over the weekend so will compare it's temp to that of the plenum and intake pipe.

If it is noticeably hotter, I will look into it.

Edited December 11, 2009 by iamhe77