Modding Upper Plenum

[Cr33do]

Hi Folks,

Im interested in improving airflow of the 182 Upper plenum by repositioning the throttle body to a similar position to the 197 inlet.

See my artistic impression below

Obviously the coil pack would need to be repositioned and a certain ammount of fab work required to achieve this but I think it could be possible. I know from flow benching our matched RS lower that isnt restricting much and also the upper runners work quite well too. We bench tested this part of the Upper and it didnt restrict flow at all:

Flow wasnt reduced either by the throttle body size, more its position and the right-angle flow required from TB to runners.

Why not just fit a 197 inlet? Well, despite my best efforts, I can see people have fitted these (to 197 heads) but cannot find specific details on what is required to make them fit a 182 head. Is it a case of drilling and tapping a couple of extra holes in the head or are they ALL different. Are the port shapes the same or is a lot of matching required. We have a polished 182 head already and it has a well matched RS lower - hence my idea of improving the 182 upper.

Any ideas, or confirmation on 197 inlet fitment to 182 head would be much appreciated.

Finally, this is for a track car with cams and high-comp pistons. I know its not going to make a huge difference but every little improvement helps and i wouldnt mind trying something different.

Cheers,
Nick

 

[Donny_Dog]

I wouldn't bother modifying the uppper plenum IMO.

Judging by previous explorations, the RS2 design seems to be the ideal setup - apart from it costs a few quid. Essentially modifying the plenum to be front mounted like ITB's you benefit from not dragging the cold air over and around a hot engine. I don't think there is more than 8bhp in it (or so I read) and maybe more with a remap, but I'm 99% sure the JMS designed RS2 did not need you to reposition sensors etc - although the mounting of the coil pack required a plate - can't remember, but do a search if you're serious.

 

[Cr33do]

Yes. Looked at RS2 kit and must say I am pretty impressed by the quality of the design and build. However, I don't want to spend that much money. Modding a 182 inlet won't cost that much except time.

Its just interesting that Renault chose to change the throttle body angle when revising the engine for the 197 etc

 

[steviet]

Is the reason the 197 inlet wont fit not something to do with the breathers?? IMO, if you can weld well enough and have a spare lying around, why not..... Nowt to lose!

 

[Cr33do]

Possible reason I suppose.

We do have a spare to play with before scrapping our matched upper. As you say nothing to lose

 

[NorthloopCup]

To fit the 197 inlet on to a 182 head you need to drill and tap the cylinder head. It's only 2 bolt holes that need tapping though so not a real issue if you have the necessary tools.
The real issue comes with the ports. Let's just say they're different to say the least. Very different. The reason why I know is because I've done this mod. It's a LOT of work.

 

[Meek_racing]

Are the 197 ports alot bigger? If so, could you use a 5 or 10mm adaption plate that blends the two profiles together? Tapping the head wont be an issue, the engine is still in bits atm.

 

[Cr33do]

To fit the 197 inlet on to a 182 head you need to drill and tap the cylinder head. It's only 2 bolt holes that need tapping though so not a real issue if you have the necessary tools.
The real issue comes with the ports. Let's just say they're different to say the least. Very different. The reason why I know is because I've done this mod. It's a LOT of work.

Superb answer! Just what I was looking for! Thank you.

Now I know the ports require so much work that's giving me more reason to modify what we already have. Need to take some measurements to see what's achievable and what other things might need to be moved.

Cheers.

 

[NorthloopCup]

Are the 197 ports alot bigger? If so, could you use a 5 or 10mm adaption plate that blends the two profiles together? Tapping the head wont be an issue, the engine is still in bits atm.

It's all about the shape and position of the ports, but yes you could use a adapter plate of some sort. I'm not convinced the gains would warrant all the effort either.

 

[NorthloopCup]

Superb answer! Just what I was looking for! Thank you.

Now I know the ports require so much work that's giving me more reason to modify what we already have. Need to take some measurements to see what's achievable and what other things might need to be moved.

Cheers.

The real issues with the original plenum are the internal design btw. Improvements can be made to the original if you know the areas to work on.
If you angle the throttle body the way you've got it, are you sure that it will clear the bulkhead? The 197 inlets are shorter in length but greater in diameter internally.

 

[Jonny1*2]

Reservoirs would need relocating I'd imagine. Have you thought about getting the inlets fully polished internally? Widening the ports may not provide gains, but a bit of work on the exhaust side to complement might be worth looking at. My standard inlets are maxed out now Nick. They are ported more than most, but due to the plenum shape, porting completely is very hard and requires special tools so Rick Wood informs me.

Ps. If you need a cheap set to practice on just holla

 

[NorthloopCup]

Forgot to say as well, you need to cut the webbing out from under the bonnet with the 197 inlet fitted!! It touches otherwise.

 

[Cr33do]

Getting some pretty good info in here now. thanks guys!

@NothloopCup - Looking at photo's on the net i did wonder if the 197 was shorter than the 182 plenum. It certainly appears to stop shorter in comparison to the rocker cover. I will need to measure the space around the bulkhead to see what is possible, but there's little point in doing it if i need to put a very sharp inlet hose before the throttle body Kinda just moves the problem...

@Jonny1*2 - Would definatley need to move the header tank. Our upper is matched to the lower ok but the polishing is quite restricted to the first couple of inches. It was interesting that the flow (bench test) didnt decrease when we introduced that cut in half upper. Only the complete upper reduced flow quite a bit. As a side point - we removed the TB and actually decreased the TB opening (using plasticine) and the flow didnt reduce. Almost proves the actual TB is able to flow sufficient air but the design of the plenum collector/TB position is inefficient.

Suppose i could cut the thing in half - polish the lot a weld it back up

Will keep on thinking about it.

 

[Cr33do]

Oh - Jonny, I think its about time we knew some more details about the upgrades you/TDF have been doing to your car Spill..

 

[NorthloopCup]

the design of the plenum collector/TB position is inefficient.

You can improve it like I said, but altering the position of the throttle body won't see any real significant improvement. Unfortunately the real restriction is the original design. And that's nothing to do with the length of the runners either just in case that's what other people are thinking!

 

[Jonny1*2]

Oh - Jonny, I think its about time we knew some more details about the upgrades you/TDF have been doing to your car Spill..

Still waiting on some bits, but I'll update you shortly

How does the bench flow work? Is it a pressurised system?
Surely the main way to improve the inlets is increasing their size and allowing more air volume to be contained?

 

[NorthloopCup]

How does the bench flow work? Is it a pressurised system?
Surely the main way to improve the inlets is increasing their size and allowing more air volume to be contained?

It's not a pressurised system, just a air pump that pumps a given amount of air through the cylinder head. Then the out going air is measured with a manometer to give you your answers. (That's a basic easy to understand description btw)

 

[Will.]

Try it. YOu can get upper inlets for like £30.

 

[sprintcup]

Would it be possible to cut the top part of the plenum off, the section with the Renault Sport logo cast into it as it looks like a flat plate, this would then give you access to the ports for machining the full runner on both sides, then you could make a 6mm ali plate and bolt it back on with a gasket and tap the peice with the Renault logo back onto that to keep the OE look.
I'm interested in this as I'm going the same route as Jonny and a few others.

Regards Russ......

 

[Chip-mk1]

Very difficult to get a small gain by doing what you are doing in terms of repositioning the inlet I would think, but potentially quite easy to make the flow to the cylinders unevent and result in a loss of power.

I think you have a lot more chance of making it worse than better realistically.

 

[NorthloopCup]

There is no reason to change the position of the throttle body at all anyway.

 

[NorthloopCup]

Would it be possible to cut the top part of the plenum off, the section with the Renault Sport logo cast into it as it looks like a flat plate, this would then give you access to the ports for machining the full runner on both sides, then you could make a 6mm ali plate and bolt it back on with a gasket and tap the peice with the Renault logo back onto that to keep the OE look.
I'm interested in this as I'm going the same route as Jonny and a

Regards Russ......

Easier ways than that to get results imo. You'd be better off cutting and re-welding, then smooth back the welds if you want to keep oem look (which is what I prefer as well personally.)

 

[Jonny1*2]

It's not a pressurised system, just a air pump that pumps a given amount of air through the cylinder head. Then the out going air is measured with a manometer to give you your answers. (That's a basic easy to understand description btw)

I assume the plenum has a pressure gradient to atmosphere, causing the flow of air into the chamber? If there is a way to increase the pressure cascade, ie. Increase the plenum volume, reducing the pressure. Making the air flow faster.

I don't do engines, but that's how it makes sense in my head. Apologies if it's nothing to do with any of that.lol

 

[Scott_r888]

imo leave it alone. you can do degree's in plenum design alone, if you were really good enough to improve on a manufacturer designed upper plenum and or plenum chamber then you'd most likely be working for motorsports/performance /f1 team. of course if you go for it and get a gain that is worth all the effort, then hats off to you. Good luck though.

 

[Cr33do]

Well this thread has certainly mmade me think if nothing else

I wondered if Chip would comment on it as I know he has done this type of thing before- custom inlets etc. I take on board that by moving the TB I could risk creating an uneven distribution of air to each runner. Something I don't want.

Northloop has hinted that the original can be improved without moving the TB. I can only deduct that the area to improve is the "trumpet" opening of each runner, accessible only by way of cutting the plenum up. Maybe slightly increasing the size of each and smoothing the transition as much as possible. Might do it.

Last question. Am I right in thinking the collector box volume is required to provide enough air when the TB is snapped open? If so, reducing this would be negative. However, if the volume was increased say by 150% would this also be negative. I.e. can you have to much volume? Just thinking aloud here.

 

[NorthloopCup]

If you look at the internal design of the rs2 plenum/intake runners and compare it to the original 1*2, you will see the area you need to improve. A increase in volume will give some improvement but the main area to concentrate on is reducing the turbulence from the air entering the runners.
Effectively you don't have enough space to reduce the turbulence around the throat of the port due to to the original design and how it sits on top of the cam cover.

I've played around with enough inlets in my time so have a good understanding of what works and what doesn't.

 

[Dan519]

Very similar has been done, about 8 years ago. Gains were minimal, and it was eventually removed in favor of throttle bodies.

The same set turned up a few months after removal, sold privately, and again gains were minimal when fitted to another car.

You're best of with just normal matching IMO

 

[Chip-mk1]

Well this thread has certainly mmade me think if nothing else

I wondered if Chip would comment on it as I know he has done this type of thing before- custom inlets etc. I take on board that by moving the TB I could risk creating an uneven distribution of air to each runner. Something I don't want.

Northloop has hinted that the original can be improved without moving the TB. I can only deduct that the area to improve is the "trumpet" opening of each runner, accessible only by way of cutting the plenum up. Maybe slightly increasing the size of each and smoothing the transition as much as possible. Might do it.

Last question. Am I right in thinking the collector box volume is required to provide enough air when the TB is snapped open? If so, reducing this would be negative. However, if the volume was increased say by 150% would this also be negative. I.e. can you have to much volume? Just thinking aloud here.

If you have too big volume then when you move the throttle drastically it will lead to a delay before the engine sees the change, so if you had a massive plenum and shut the throttle the engine would still rev for a second till it exhausted the plenum capacity, then when you snapped the throttle open the pressure in the inlet ports wouldnt equalize until after the plenum had done so.
So yes you can definately go too big in terms of drivability, but in terms of flat out performance the bigger the better generally speaking.
The final runners to the head are the key thing though for breathing potential of the engine, and the optimum will be different at different RPMs.

The RS2 is the ultimate compromise in this respect for a standard engine, 150lbft for the entire rev range is obviously awesome, but on the flip side the peak is also 150lbft, where as the standard inlet for example will give 165lbft potentially for a very small window around the 5500rpm point, so at that point the standard inlet is better, but its then a bit gash everywhere else. If its well ported then you can move that sweet spot up the range a little, which improves horsepower as a result.
Throttle bodies will be great at the top end, but nothing like as good lower down as the RS2, if its a pure track car, this is the way to go.