Hey folks, as most of you know I'm currently awaiting my new motor to be built, and I've previously run a motordyne 5/16" isothermal spacer with success. What I'd like to know is if anyone has played around with the stock plenum and also a plenum spacer on the same car, and measured if there are any gains to be had while boosting 12+psi.

So far I've had mixed feedback to the question, some people saying that it provides little or no gain while boosting, while others stating they swear they've gained power with the spacer alone. Also, I'm concerned that gains may be diminished with higher boost levels, as the manifold is pressurized to the point where the added flow of the spacer is negated.

I don't think it will be a leak issue, as I know people have run these spacers past 500-600whp.

So let's hear it. Is the spacer a go or no-go?

 

i have tested it on two 500 plus cars and it didnt make a difference at all, both cars had some small sort of boost leak, turned out to be the BOV on both of them, we took out the plenum spacer to see if that was causing it and it didnt make any difference.

 

In my opinion, the spacer would add power. The additional volume should help keep the plenum from choking up. Too small a plenum and it will "choke" things up. Too large and it will be inefficient. I believe people have done before and afters on boosted set-up. I'm too lazy to search right now but, someone can probably post the link.

 

I'm referring to a built setup in particular. I'm fairly positive it made power on my stock motor setup but I didn't do a before/after the same day.

 

I know this isnt dyno proof but I'll share my thoughts. As you know Ive been running a Crawford plenum that cracked on the way to Z day Z. Now I have a stock plenum with no spacer. At first I felt no difference, but after a few days of driving my car, I noticed only way up top in 4th and 5th that IMO it felt slower. Remember I have a 3.3FD and the gears are much longer so the difference may not be as pronounced with the stock gearing as 500whp will always feel quick. With that being said Sharif said he has ssen less than 5whp difference with plenum/spacer vs stock, but Im ordering a 1/2" spacer this week. For the $$$ why not?

 

weird cause on my dyno, i have seen the crawford plenum cause some weird stuff at the top of 5th gear. i actually took it off my all motor car for that reason, i have seen it on a couple other 1:1 ratio pulls up top.

you need one of my top secret plenums man, there is only one in the world right now

 

Well if you wannsa hook me up you know I'll test it where it counts

 

At high or low boost, you are looking at about 8-10whp maximum from the current crop of spacers and plenums. If you have a spacer, and are happy with it, I would just keep it.

 

Does anyone have any feedback/experience with the MREV2 on a FI'd engine? I was thinking about throwing one into the mix to see if it will give me a little bit more power up top.

 

If it keeps the same characteristics as on an NA Z, it will increase midrange TQ and power, but actually lose power from 6500-7000rpm's, at the very best it will retain the same power as before. If you want power from 6000rpm's up, MREV2 isnt for you.

 

Yeah I don't really see a big reason to take it off the car if it's worked in the past. If I could just get rid of it and run my strut tower bar without spacers or anything it might be nice. I'll probably just opt to keep the spacer on there.

 

good call on keeping it ...
i mean why not right

 

Spacers are cheap. Even if it's only 5-10 hp, a couple of hundred bucks isn't that much in the FI game. Especially if you've already got one laying around.

 

My main concern is the fact that it causes my STB to slightly rub on my hood. I can live with it but its slightly annoying.

 

LOL

so, is it "one of"
or is there "only one"

for the price bro, it couldn't hurt to get a used one and test it. If it doesn't help, then you can re-sell for a very small loss, if any at all.

 

Is it audible? Or is it just visual when you open the hood?

 

Just visual (my hood is fiberglass too). I've had to reclear my strut brace once and it VERY SLIGHTLY rubs now. It actually rubbed on the square flange on the turbonetics intake piping where it meets the MAF housing. We're actually chopping that flange off during the build so I'm pretty sure I'll be able to grind down the spacers and have it sit a few mm lower for clearance.

In the past i've been running rubber weather stripping on the underside of the hood and putting black tape around the strut brace to keep it from getting too messed up.

 

If there's a clearance issue I'd toss it... Gains don't justify the headaches associated with it IMO.

 

i think there are smaller washer out there this days you can use for your hood

believe it or not my plenum spacer cleared my VIS FUsion hood which is not so good on clearance also

 

From all the tests I've seen, the spacers will add about 17-20 HP when boosted.

There have been several dyno plots posted here in the past. Mike (350ZNV / SincityZ) made a thread on one a while ago. There were test results posted by RandysG and ZBOY too. They were all in the 17-20 range.

As for clearing the fiberglass hood, it may be easier to try a short stack of washers as opposed to grinding down the MD strut bar spacers.

Let me know if you would like to do a pre/post test on your new engine build. One more data point would be good to see.

Tony