Plenum Spacer Comparison
05-20-2005, 10:42 AM
#1
Plenum Spacer Comparison
FOREWORD. This is one man’s review of two recent-to-market products, the Altered Atmosphere (AAM) angled and the Motordyne Engineering (ME) 1/4” plenum spacers. I’m posting this review because I feel it is my responsibility to the board as I am likely the only one to have installed and driven both on the same car.
PURCHASE. I purchased the AAM (retail $249) during the initial group buy and got mine late enough in the cycle to receive the revised bolt lengths and instructions. The ME (retail $195) was acquired through a trade agreement with Tony for the AAM unit, as he plans on doing the side-by-side dyno test comparisons that I was unable to do.
BUILD/QUALITY. Both spacers are CNC milled from 6061-T6 Aluminum, the primary difference being the AAM is a solid piece whereas the ME unit is joined from two pieces. I imagine the latter allows the piece to be cut from a smaller “blank” with less waste, thus saving material cost. ME assures no loss of strength and both manufacturers recommend their product with forced induction (FI) applications. The ME spacer is 1/4” thick throughout while the AAM angled spacer is just that, angled from front to back—1/2” to 1/4”. Both are designed to increase air volume, primarily to the front cylinders, which become starved at high rpm.
The angled spacer follows suit with full upper plenum replacements like Crawford and Kinetix, which are designed to even out air distribution to all cylinders. The angle, however, precludes the use of spacers, included with the ME unit, which offer support for the 6 interior plenum support posts.
The AAM contact surfaces appear finished to a higher degree of polish while the ME had some visible but not feel-able machining marks. The exterior of the AAM unit is left unfinished while the ME is grit blasted to better blend in with the OEM sand-cast plenum.
A complete set of new bolts, washers and machined spacers are included with the ME unit for both the spacer and the strut tower bar (STB). The AAM reuses some of the OEM plenum bolts and all of the STB bolts, the supplied spacers of which are comprised of stacked washers. The one-piece ME STB spacers were grit blasted as well and much easier to install without dropping. Not that many would notice, but they actually look great too compared with the stacked washers.
INSTALL. I will not go into excessive detail here, as I believe both units are relatively easy to install when armed with common sense and a modicum of mechanical ability. I will say that the AAM required a trip to the hardware store in search of longer bolts, rubber gaskets and washers, as I was unable to get an airtight seal to the before-mentioned interior bolts with the supplied washers.
The ME comes with adhesive gaskets that you affix to the plenum post supports/spacers, which are then stuck to the interior plenum posts during the install. This provides a solid base upon which to torque the center bolts and exhibited no leaking. The AAM, as mentioned before, is not supported in this fashion due to the angled design but does retain the six stock bolt locations. I’ve been assured that the plenum will not flex and one can point out that the Kinetix doesn’t use any, but I still like the idea of additional support under the pull of that huge vacuum we call the VQ35.
Following AAM’s instructions, I initially tried two washers on either side and had vibration issues when the engine would come into contact with the STB. After adding additional washers to the driver’s side and increasing tension to bow the STB upwards, I was still experiencing vibration. More so when the car was hot, the A/C was on and when turning left. I was at the limit for hood clearance at that point and accepted the fact that build tolerances vary from car-to-car and I had one of those cars. This is an unlivable circumstance which can be resolved a number of ways, mine being the decision to use the ME unit which maintains a large amount of clearance on the first try with zero vibration tinkering.
DYNO/POWER. I realize some community members would love to see an unbiased and conclusive dyno comparison, but I believe the power differences would be so minimal as to be quite difficult to measure (well-within the error range of most dynamometers) and therefore inconclusive. There are certainly enough differences to make an informed purchase decision based on more than power alone. That being said, both manufacturers claim similar power gains and as with all breathing mods, gains are dependant on other mods you have installed.
My personal impression is the 1/4” ME gives up a little to the AAM towards redline. Looking at the dynos for the AAM, you can see the power increase is more-or-less constant to about 80 and then increases from 80-100mph. The ME feels more linear and would likely be represented on the Dyno by a more parallel power path to redline.
CONCLUSION. Spacers are a great compromise to a full upper plenum replacement and provide a nice boost in power throughout the entire rpm range for a modest investment and with stock-like appearance. My conclusion is that if a stealth install is desired, as it was in my case, the ME spacer is the way to go. At $55+ less than the AAM (adding in $6 for misc. washers and bolts) it is a better fitting product that works right out of the box. For those going for maximum HP numbers and unconcerned with hiding the modification, I’d consider putting the $200-250 you might spend on a spacer into the Crawford cast plenum and a new strut tower bar knowing that you likely have the maximum power available from such a modification and no reliability issues.
I have nothing but best wishes for both manufacturers, as anyone that makes products for this car (and for this crowd of discriminating enthusiasts) deserves an award in my book. They are obviously not in it only for the money and we are lucky to have competition in such a specialized niche market. Good luck to them both as I’m sure they will only improve their product offerings as the market matures!
LINKS.
http://www.motordyneengineering.com/350z.asp
http://www.alteredatmosphere.com/350z_1.asp
PURCHASE. I purchased the AAM (retail $249) during the initial group buy and got mine late enough in the cycle to receive the revised bolt lengths and instructions. The ME (retail $195) was acquired through a trade agreement with Tony for the AAM unit, as he plans on doing the side-by-side dyno test comparisons that I was unable to do.
BUILD/QUALITY. Both spacers are CNC milled from 6061-T6 Aluminum, the primary difference being the AAM is a solid piece whereas the ME unit is joined from two pieces. I imagine the latter allows the piece to be cut from a smaller “blank” with less waste, thus saving material cost. ME assures no loss of strength and both manufacturers recommend their product with forced induction (FI) applications. The ME spacer is 1/4” thick throughout while the AAM angled spacer is just that, angled from front to back—1/2” to 1/4”. Both are designed to increase air volume, primarily to the front cylinders, which become starved at high rpm.
The angled spacer follows suit with full upper plenum replacements like Crawford and Kinetix, which are designed to even out air distribution to all cylinders. The angle, however, precludes the use of spacers, included with the ME unit, which offer support for the 6 interior plenum support posts.
The AAM contact surfaces appear finished to a higher degree of polish while the ME had some visible but not feel-able machining marks. The exterior of the AAM unit is left unfinished while the ME is grit blasted to better blend in with the OEM sand-cast plenum.
A complete set of new bolts, washers and machined spacers are included with the ME unit for both the spacer and the strut tower bar (STB). The AAM reuses some of the OEM plenum bolts and all of the STB bolts, the supplied spacers of which are comprised of stacked washers. The one-piece ME STB spacers were grit blasted as well and much easier to install without dropping. Not that many would notice, but they actually look great too compared with the stacked washers.
INSTALL. I will not go into excessive detail here, as I believe both units are relatively easy to install when armed with common sense and a modicum of mechanical ability. I will say that the AAM required a trip to the hardware store in search of longer bolts, rubber gaskets and washers, as I was unable to get an airtight seal to the before-mentioned interior bolts with the supplied washers.
The ME comes with adhesive gaskets that you affix to the plenum post supports/spacers, which are then stuck to the interior plenum posts during the install. This provides a solid base upon which to torque the center bolts and exhibited no leaking. The AAM, as mentioned before, is not supported in this fashion due to the angled design but does retain the six stock bolt locations. I’ve been assured that the plenum will not flex and one can point out that the Kinetix doesn’t use any, but I still like the idea of additional support under the pull of that huge vacuum we call the VQ35.
Following AAM’s instructions, I initially tried two washers on either side and had vibration issues when the engine would come into contact with the STB. After adding additional washers to the driver’s side and increasing tension to bow the STB upwards, I was still experiencing vibration. More so when the car was hot, the A/C was on and when turning left. I was at the limit for hood clearance at that point and accepted the fact that build tolerances vary from car-to-car and I had one of those cars. This is an unlivable circumstance which can be resolved a number of ways, mine being the decision to use the ME unit which maintains a large amount of clearance on the first try with zero vibration tinkering.
DYNO/POWER. I realize some community members would love to see an unbiased and conclusive dyno comparison, but I believe the power differences would be so minimal as to be quite difficult to measure (well-within the error range of most dynamometers) and therefore inconclusive. There are certainly enough differences to make an informed purchase decision based on more than power alone. That being said, both manufacturers claim similar power gains and as with all breathing mods, gains are dependant on other mods you have installed.
My personal impression is the 1/4” ME gives up a little to the AAM towards redline. Looking at the dynos for the AAM, you can see the power increase is more-or-less constant to about 80 and then increases from 80-100mph. The ME feels more linear and would likely be represented on the Dyno by a more parallel power path to redline.
CONCLUSION. Spacers are a great compromise to a full upper plenum replacement and provide a nice boost in power throughout the entire rpm range for a modest investment and with stock-like appearance. My conclusion is that if a stealth install is desired, as it was in my case, the ME spacer is the way to go. At $55+ less than the AAM (adding in $6 for misc. washers and bolts) it is a better fitting product that works right out of the box. For those going for maximum HP numbers and unconcerned with hiding the modification, I’d consider putting the $200-250 you might spend on a spacer into the Crawford cast plenum and a new strut tower bar knowing that you likely have the maximum power available from such a modification and no reliability issues.
I have nothing but best wishes for both manufacturers, as anyone that makes products for this car (and for this crowd of discriminating enthusiasts) deserves an award in my book. They are obviously not in it only for the money and we are lucky to have competition in such a specialized niche market. Good luck to them both as I’m sure they will only improve their product offerings as the market matures!
LINKS.
http://www.motordyneengineering.com/350z.asp
http://www.alteredatmosphere.com/350z_1.asp
05-23-2005, 06:10 AM
#5
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now that i have had the aam spacer and now the crawford cast plenum i can say that they are very close in power. i do however, like the crawford setup better because it seems to seal better (no vacuum leaks) and although i had to change the strut bar i don't have to worry about clearance issues with the hood or plenum. also, you have all the correct hardware (they supply the two upper plenum bolts with locktite and teflon washers - these seem to seal better than the rubber washers with aam) as you use all of your stock plenum bolt hardware and relocate clamps.
the only downside, if you want to call it that, is that you must buy a strut bar that will work with the crawford plenum and you cannot use your engine cover unless you modify it. however, with the crawford plenum & strut bar + no engine cover the engine bay does not look that bad.
not trying to steal the thread here but sounds like the md might be a better setup....but since i have not had the kit or seen it in person i cannot comment
the upside is that there are significant gains to be had here with the spacers or the plenum....that is for sure
someone should do a review of all three....that would cover all bases...but i don't think you can go wrong with any of them as far as power is concerned
later
the only downside, if you want to call it that, is that you must buy a strut bar that will work with the crawford plenum and you cannot use your engine cover unless you modify it. however, with the crawford plenum & strut bar + no engine cover the engine bay does not look that bad.
not trying to steal the thread here but sounds like the md might be a better setup....but since i have not had the kit or seen it in person i cannot comment
the upside is that there are significant gains to be had here with the spacers or the plenum....that is for sure
someone should do a review of all three....that would cover all bases...but i don't think you can go wrong with any of them as far as power is concerned
later
05-24-2005, 08:05 AM
#7
Great review 350Zenophile 
I agree with you on all points made and your assesment of all the products is very fair... If I was looking for a better intake solution including ALL the factors at this point, I think I would opt for the Crawford or APS tall boy, even though you have to buy a new STB.
I bought the AAM Spacer when they had the GB and with the new hardware ($20-25) and patients with the install, it's been a successful solution for me with the new found power and stock look
IMO, either way you go, new plenum or spacer you will enjoy the results!
Zquicksilver
I agree with you on all points made and your assesment of all the products is very fair... If I was looking for a better intake solution including ALL the factors at this point, I think I would opt for the Crawford or APS tall boy, even though you have to buy a new STB. I bought the AAM Spacer when they had the GB and with the new hardware ($20-25) and patients with the install, it's been a successful solution for me with the new found power and stock look
IMO, either way you go, new plenum or spacer you will enjoy the results!Zquicksilver
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