My disappointment with Motordyne's plenum spacer
 

Motordyne just happen to be the brand I purchased, so my post would most likely apply to any brand.

I'm disappointed because of two things.

1) I didn't get any discernable performance increase.
2) My AVG MPG went down 1 mile per gallon.

I did a lot of research on this before buying. It really seamed like a slam dunk for a cheap mod. But, now I'm sorry I purchased it and will at some point pull it off and sell it to the next sucker.

Does anyone have any ideas why the mod didn't seem to produce any positive effects?

Now, to be fair, I didn't do any time trials or Dyno tests before or after...just simply didn't notice any acceleration difference at all RPM's up to RL. Maybe 15 HP increase wouldn't be noticed, but it seems like it should.

I have a 2004 stock 350Z No other mods have been done to the car...i.e., factory air cleaner and exhaust etc.:mad:

I never heard of any bad things about Motordyne's spacers. Which one did you purchase? As I recall, there are different combos that work for revups and non-revups.

I bought this one off Amazon...

Without a baseline dyno to work from, you have no way of knowing if there was any increase. What were you expecting? Even if you got a 5-7 HP increase with the plenum spacer, you'll never feel that with your butt. It seems like you had unrealistic expectaions before you even started this mod.

Ya, that's kind of what I feel now....I probably wouldn't have noticed the HP increase in the butt, but If anything, I didn't expect that the MPG would go down....if anything you'd think it would go up as the mod makes the intake more even and efficient.

Did you reset your ecu? Spacer/tp/ tune are what's going to give you biggest gains even on the butt dyno

what other mods do you have? you might need a tune to take full advantage of them.... and even still the gains will be minimal

Read post #1 again- OP says he has no other mods...

doh, my bad..... still half asleep this morning

This is the problem. And your mpg went down based off of what? The dash guage? I wouldn't trust that to be accurate. Get a k&n drop in filter and leave the spacer on, leave your negative terminal disconnected over night (assuming you just put it on) They say you can't feel anything under 10hp difference, and you won't get more than 10hp from just a plenum spacer without any tuning.

The mod wouldn't have so many good reviews and proven Dino tests if it was snake oil.

How about that tune though? :icon17:

on a non rev up, the spacer and even a mrev2 plenum will hardly do anything... or even the combo, but you'll feel the spacer moreso... your mpg went down because you're using more air, which leads me to believe you are feeling something to be accelerating more. a spacer on a rev up helps the cylnder 1&2 starving at higher rpms... the mrev2 on a rev up does the same... but now that you've added the spacer the next mods will have more affect than them alone.

I'll give you $25 shipped for it

$30 shipped

$40

A common misconception with performance mods is that mpg will improve. There IS some truth to this, but by increasing the efficiency of the intake manifold you also increase the amount of fuel that is needed to compensate for that.

Your drop in mileage is most likely as a result of you having a bit more of a lead foot to "experience" your new upgrade. Drive like a granny and im sure your mileage will go back to normal.

As for a reflash, its recomended with this mod to get the "full effect". however its up to you if you want to justify dyno fees and tuning fees just for 5hp.

Take it in stride my friend lol

if you are seeking actual and measurable performance gains from NA bolt-ons to a VQ35DE 350z, expect nothing but disappointment.

You need an unrealistically positive attitude and a real generous/optimistic ass dyno to find any enjoyment down that path.

Focus on making it fun to drive and nice sounding... because faster at all (to any relevant measure) is not going to happen. If you want fast, then you want boost.

I second this motion brah

1mpg is a very small margin for error.. I mean it could be due to weather, the way youre driving, city to highway ratio... wind lol. I mean come on 1mpg? now if it was 5 to 10 id be concerned.

You know what? Your car will decimate all, after, you put about fifteen grand in it or more. If you have to, overnight parts from Japan.