Intake Spacers, worth it or not?

[P_G]

I've seen these around for a while and whilst consideinrg getting mine decoked I wondered about putting these in as well. Question is, is it worth it. The theory appears to be there but in practice, will it reduce manifold temps so much that you get denser air and then more torque / bhp?

I read what JHM have on their site and take it with a liberal pinch of salt because they are trying to sell them so what are other peoples interpretations?

[sonny]

Iv been running with the 10mm phenolic JHM spacers for a few months now, the real benefit of these is performance longevity, they will keep the inlet manifold around 20% cooler than the engine block thus not heating the air up as much. There is no increase in performance. But will keep you going at peak performance longer esp on track.

The manifold is still hot to touch but not as hot as the engine block. Would be interested to test it with a thermal gauge.

Are they worth it or not........If your into tracking your car then Yes. Day to day, No (unless you get them at a good price).

[adsgreen]

agree with sonny - same as CAI really. won't give you more but let you keep what you've got for longer.

[Rick_RS4]

i had one on my 1.8t it made a difference to the inlet mani temp quite alot, but driving wise you wont notice you installed it, if you are doing that its worth doing the throttle body water jacket blank too, and id consider the gold heat reflective hood for under the inlet mani,

every little helps

[sonny]

Is that the "bag of ice" water jacket Rick? where's Danny when you need him lol

[S4Player]

I have the jhm spacer as well the ice was used to see the effects of heatsoak at the rr day was a worthwhile exercise

[ArthurPE]

the air is moving pretty fast in the manifold...at 7500 rpm ~ 550 ft^3/min
what's the volume of the manifold? <1 ft^3 if that
so it exchanges volume 550 times per minute or 9 times per sec...very little contact time to do heat transfer...
does increasing the volume with the spacers give more contact time, at perhaps a lower temp, ie, off-setting gains, 0 net change

how much cooler do the insulators make the manifold? (easy to check, 2 cars, same day, one with, one w/o, run same time, same temp, pull over and check the temp with an IR thermometer)
do they make it hotter?
does being in contact with the block (albiet with a gasket insulator) allow the cooling system to conduct heat from it?
will lengthing the tract affect performance? i mean Audi picked a given length for a reason...

[sakimano]

the spacers are around $200 USD...and trusting the company that makes them and their research it's hard not to buy them.

It's a weird mod that is hard to justify, no matter how much math you do. That same math(ematician) says carbon buildup doesn't impair performance. Fine...that's one person's opinion...and it looks like he won't be sold on spacers.

You kind of just have to trust it. I had them on my S4 and I can't say I noticed that they worked, because it's one of those 'every little bit' or 'sum of the parts' mods, and I trust that they do help, so I installed them. I can say 'heat soak' at a track event or dragstrip day was less of an issue for my car than it was for friends without the spacers...and that could be seen with our timeslips.

Could be a million things I guess. Race teams use them (and have for ages), and JHM says they work. The amount of products they've designed, built, tried and then scrapped is long enough that I trust them to toss the turkeys and promote the winners. This is one of the (little) winners. On a platform where the manifold is off and on just about every year or two, may as well fit them in.

[P_G]

the air is moving pretty fast in the manifold...at 7500 rpm ~ 550 ft^3/min
what's the volume of the manifold? <1 ft^3 if that
so it exchanges volume 550 times per minute or 9 times per sec...very little contact time to do heat transfer...
does increasing the volume with the spacers give more contact time, at perhaps a lower temp, ie, off-setting gains, 0 net change

how much cooler do the insulators make the manifold? (easy to check, 2 cars, same day, one with, one w/o, run same time, same temp, pull over and check the temp with an IR thermometer)
do they make it hotter?
does being in contact with the block (albiet with a gasket insulator) allow the cooling system to conduct heat from it?
will lengthing the tract affect performance? i mean Audi picked a given length for a reason...

As a whole I agree but you last comment, Audi picked a given length for a reason, and the reason unfortunately is not always to extract the most performance within safe tolerances, more likely the budget given to develop the car. Hence why you can get uprated ARB's, lighter wheels, more flow efficient intake hoses, better brake lines one aux rad. that has the efficiency of 2 etc etc.

I won't be buying JHM ones as we have someone locally who is going to manufactur them and this is likely to be cheaper than the JHM ones inclusive of carriage and duty and of the same quality if not better knowing what work he has done for me and others in the past.

[ArthurPE]

I doubt they help, but probably don't hurt
remember, thermo calcs are done in deg K, 273 + def C
so even if you drop the air charge 5 deg C, 30 to 25 (~10 F) very unlikely, that is <2% change in density, about 1.5% in HP, if that

I agree, some things like wheels etc. are cost driven, but in this case I believe it to be performance driven, and I don't mean only power, but also efficiency, flexibility/elasticity/tractablity, etc.

if temp was a huge concern a plastic piece could be used, like BMW and others do...
aluminum is a good thermal conductor, it may actually promote charge cooling

now you want some torque gains? chill the fuel using the AC compressor...more dense and will cool the air charge better during the expansion phase

[ArthurPE]

pulled out the thermo text...more heat may go into the stream with spacers...
firstly, any impact is small: air is a poor conductor so only the boundry region (surface in contact) will transfer q, most of the air will not get any warmer either way
and the faster (ie less contact time) the less gain
also the lower the delta Temp, the less transfer for a given system

but from another perspective (all steady state)
let's say the engine operates at 100 C
engine compartment air 50 C (air flow evacuates most)
and the intake air is at 30C
spacers manifold temp 85 C
w/o spacers 90 C

q transfer ratio with spacers (85 - 30 - (85 - 50))/(85 - 30) ~ 20/55 ~36 % of all q goes into the intake airstream, the balance goes out with the engine compartment airstream
w/o spacers (90 - 30 - (90 - 50))/(90 - 30) ~ 20/60 % ~33%
(terms like airflow Q, etc., cancel assumed same for both systems)

total q for the manifold
spacers / no spacers ~ (273 + 85)/(273 + 90) ~ so the spacer'ed manifold has 0.986 as much as the one w/o (all other terms cancel)
0.36 x 0.986 ~ 0.355 > 0.33, so even though the manifold is cooler (less q) it imparts a higher q (temp gain) to the air stream

[Timster]

q transfer ratio with spacers (85 - 30 - (85 - 50))/(85 - 30) ~ 20/55 ~36 % of all q goes into the intake airstream, the balance goes out with the engine compartment airstream
w/o spacers (90 - 30 - (90 - 50))/(90 - 30) ~ 20/60 % ~33%
(terms like airflow Q, etc., cancel assumed same for both systems)

total q for the manifold
spacers / no spacers ~ (273 + 85)/(273 + 90) ~ so the spacer'ed manifold has 0.986 as much as the one w/o (all other terms cancel)
0.36 x 0.986 ~ 0.355 > 0.33, so even though the manifold is cooler (less q) it imparts a higher q (temp gain) to the air stream

WTF

[PetrolDave]

WTF

Don't panic dear, it's only maths

"Real" engineers, like Arthur PE, combine a mathematical understanding with practical knowledge.

If you want an emotive debate on who is and isn't an engineer the Institution of Engineering & Technology has an ongoing letter debate about whether Sir James Dyson is an engineer or just an entrepreneur.

[sonny]

lol

[Rick_RS4]

Is that the "bag of ice" water jacket Rick? where's Danny when you need him lol

lol no, i saw there was a gold heat sheild that went over the blick and under the inlet mani to stop rising heat? cant seem to find it now