F4R flow tests

[Andrew Cooke]

Having knocked up a flow bench

https://www.rtoc.org/boards/showthread.php?t=17946

it's now time for it to earn it's keep.

It's worth pointing out that this is my bench, it's not calibrated to any kind of standard, so don't read too much into the results, or try comparing them to results you might find on the internet.

Obviously the first thing I did was see if there is any kind of agreement with any tests I could find on the internet

I found some tests preformed by Guy Croft, if you don't know who he is let Google be your friend. Needless to say he's been building engines for a while, undoubtedly knows what he's doing, has a professional flow bench, and will no doubt have it correctly calibrated. You will also find his results on the CNCheads website. I don't have the numbers, just what I could estimate from the graph and squinting in that special way...

Without further adoo:


I was gobsmacked, different heads, different benches, days etc. I guess my bench is working OK

[Andrew Cooke]

Today's tests were with the standard inlet plenum, or more specifically to see how much the standard inlet restricts things. I think it's reasonable to say that fitting individual throttle bodies onto a 172 finds around 20hp. Assuming that these ITBs are well designed they will probably only loose a couple of CFM over the bare head.

The three tests here are bare head, standard lower manifold fitted, then standard lower with standard plenum.


If the weather is OK tomorrow I'll pull the RS lower off the Twingo and test that. Looks like I'll be running around with the standard lower for a bit

Anybody fancy guessing what flow figures I'll get at 11mm lift with the RS inlet?
to get you started bare head = 129.5, head with standard lower = 117, standard lower with standard plenum = 111.6CFM.

[Scoff]

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Anybody fancy guessing what flow figures I'll get at 11mm lift with the RS inlet?
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I'll hazard 122cfm

It's getting very interesting for me now

[Andrew Cooke]

------
Anybody fancy guessing what flow figures I'll get at 11mm lift with the RS inlet?
------

I'll hazard 122cfm

It's getting very interesting for me now

I'm going to be optimistic and say 129

[Andrew Cooke]

------
Anybody fancy guessing what flow figures I'll get at 11mm lift with the RS inlet?
------

I'll hazard 122cfm

It's getting very interesting for me now

you win

[Andrew Cooke]

RS lower tested:



Now I have a dilemma, the standard PH1 plenum is a bit smaller than the RS lower, should I start of matching that to the RS lower, or should I match the RS lower to the head?

I think I'll do the plenum first, only because I'd like to see the complete inlet with standard RS lower better the flow from the standard lower with no plenum attached...

[Scoff]

I think matching it to the head doesn't always do a right lot, or so I've read. Where's Martin gone ?

I think the runners of the top half would need to be of similar ID to the RS lower to see any significant improvement, wouldn't they ?

[Andrew Cooke]

The thing about matching to the head is that it's the de-rigeur CS mod. I'll have to do it at some point for that reason alone.

The top half will be pretty easy to match to the RS lower, it only narrows down at the very end.

[Rob@Backyardracing]

good info andy, i have the stock ph1 mani on my ph1(upper and lower), and 2x RS lower just popped up for sale on CS, think i`ll snap one up! i heard they was the better lower, but im a tad skeptical of what i read there, they do believe engines only reach tdc once every 720 degrees after all, i should the firing order of the f4r

[MFaulks]

I think matching it to the head doesn't always do a right lot, or so I've read. Where's Martin gone ?

I think the runners of the top half would need to be of similar ID to the RS lower to see any significant improvement, wouldn't they ?

I'm here, just trying to picture these setups in my mind. What are the options available with the RS hardware is it manifolds and plenum changes or head as well? Any pictures of the head port options, and associated manifolds?

From the numbers you have Andy, if the point of greatest restriction is going to be the standard plenum then as you say you need to start there. But before chopping away, are there any other changes to the plenum inside lead-in to each runner, bias, contour etc when comparing the RS? As to the manifold, if the general taper is gradual then I would leave it as this is likely accelerating the flow and preventing the onset of flow separation and turbulence. It would only need to change or be modified if the flow potential of the head out strips that of the preceding sections, then you would need to work back again. But as you mentioned earlier I think port velocities and the ability of the engine to capitalise on potentially increased flow numbers is going to become increasingly important to balance.

But out of interest, what is the bare port flow figure for your head i.e. no inlet valve fitted, as this will give you the highest peak value the complete induction system can flow in it's current configuration and as cast + cnc finish?

[Andrew Cooke]

I'll give you a couple of starters Martin:

http://www.guy-croft.com/viewtopic.p...85c80341#p7134

https://www.rtoc.org/boards/showthread.php?t=14925

I've just taken some pics, back in a bit

[Matt Cole]

Andy, have you got access to a 225 inlet to test? I hope so because it may be my next move for easy power gains.

[Andrew Cooke]

I'll start with a pic



here you can see the RS lower inlet, and a PH1 plenum.

All lower inlets are interchangeable between all 172/182s, some left the factory with RS on the casting, these are larger inside and outside than the non RS inlets.

I've not seen a plenum that came from the factory bolted to an RS lower, so can't say how well it matches, but the standard plenum has a smaller exit than the RS inlet.

A quick pic looking down into the RS lower:

[Andrew Cooke]

Andy, have you got access to a 225 inlet to test? I hope so because it may be my next move for easy power gains.

no Matt

[Matt Cole]

no Matt

mmm, i wonder if someone has one to send to you???

[Andrew Cooke]

opening out the plenum to the size of RS lower found something. I only had to go back about 20mm to get to the point where the plenum was already the right size.

[Rob@Backyardracing]

ive just got me a RS lower good knowing i only need to go 20mm into the ph1 plenum to match!

good work

[MFaulks]

Thanks for the refs and pics. Just jumped over to the cnc heads site, are the pictures featured on their site actually showing the F4R head?

Out of interest, can you / could you space the lower inlet manifold from the head, so you have a straight section and see effect at your 11mm lift i.e a sandwich plate? Start off at the manifold dimensions, get some numbers, and then start opening it up to the head contours and test again. Would be interesting to see, and would give you a sacrificial component that you can throw without necessarily upsetting either your head or manifold until you know how it responds. Just a thought.

[Andrew Cooke]

Thanks for the refs and pics. Just jumped over to the cnc heads site, are the pictures featured on their site actually showing the F4R head?

no, just some random bling, the pics on the Guy Croft link are.

Out of interest, can you / could you space the lower inlet manifold from the head, so you have a straight section and see effect at your 11mm lift i.e a sandwich plate? Start off at the manifold dimensions, get some numbers, and then start opening it up to the head contours and test again. Would be interesting to see, and would give you a sacrificial component that you can throw without necessarily upsetting either your head or manifold until you know how it responds. Just a thought.

possibly... I'm working on a spare head, so can mash it up if needed, the RS lower is one I'd use (as I've just taken it off my car)

[Ashy]

very interesting Andy, So a phase 1 head with an RS lower matched to the plenum looks like the way forward?

When I find my slippers I'm gona see if ive got an RS lower....

[SP33DY]

I have an RS inlet but its fitted to my car

[Ashy]

I have an RS inlet but its fitted to my car

I think the wife has one on the 182, not for long

[SP33DY]

[Andrew Cooke]

The graphs are getting a bit busy, so I'm going to try and split them up into something more sensible.

Today we have CS's favourite, matching the plenum to the head, obviously this isn't professional work, just my best stab at it, so results will no doubt vary.

First graph compares the different stages of lower with the bare head:


the next shows the current state of affairs, it would appear that at this point the plenum is holding things back.

and finally a comparison showing how the complete inlet compares from standard PH1 to what I have now.


The question is what to do now... I'm thinking that I might run the bandsaw through the plenum to separate the plenum box from the runners

[Tony Walker]

:S On a positive note ur atleast making good progress

[Trevhib]

Cracking work. I'm sure this thread is read with great interest/appreciated by more than those actually posting replies.

[Andrew Cooke]

This is an interesting comparison, it compares the flow through the single 34mm inlet valve on a GTT head with a single 33.5mm valve in a 172 head

It's clear that the 172 valve doesn't flow anywhere near as well as the GTT one, why might that be? My guess is it's the proximity of the cylinder wall and edge of the combustion chamber in the 172 engine.

[MFaulks]

Andy, out of interest try this, fill the redundant port and blend to a more realistic shape to remove the port divider with plasticine i.e one port, one hole down to the single valve. You will always have flow separation at the divider and likely not seeing efficient re-attach, but will be more pronounced at higher port flow velocities. Obviously you will not be able to produce a direct port to the valve, and correct the port contours, but will remove the divider influence. Can then retest and be able to judge the shrouding as a single entity than having other biasing effects associated with the 4v configuration.

[Adey aka Ewok]

has any one got a pic of the 225 inlet and will it bolt up to a 172 head?

[James5]

has any one got a pic of the 225 inlet and will it bolt up to a 172 head?

Different ports Adey,

Look at the attached pic of my old 172 lump and you can see the inlet ports


I will try and find a pic of a 225 head to show you matey

[Adey aka Ewok]

If you could that would be great

[James5]

If you could that would be great

Not the best pic but you can just about see that the 225 head inlet ports are kind of heart shaped, I will try and find another pic (GAZ2405 coupe 225 conversion)

[Adey aka Ewok]

the ports do look different, does that mean the bolt pattern and spacing are different?

[James5]

the ports do look different, does that mean the bolt pattern and spacing are different?

Shame I can't find a better pic, but I rememebr a member on here fitting the 225 head to a 172 block with very slight modification..

I am sure MAtt C, Ashy, andryg may have some better pics of a 225 cylinder head inlet port to show you the difference and the stud pattern difference.

[Adey aka Ewok]

if its that different it wnt bolt up im not to bothered, was hoping for a short inlet setup on the cheap, dnt want to go as far as swapping the head for it tho, cheers buddy

[James5]

if its that different it wnt bolt up im not to bothered, was hoping for a short inlet setup on the cheap, dnt want to go as far as swapping the head for it tho, cheers buddy

Much better pic from ilkers project thread, and you can see the stud patterns are very different and the port inlet's are very different aswell

[Matt Cole]

Shame I can't find a better pic, but I rememebr a member on here fitting the 225 head to a 172 block with very slight modification..

I am sure MAtt C, Ashy, andryg may have some better pics of a 225 cylinder head inlet port to show you the difference and the stud pattern difference.

Yes they are different matey. Exhaust is a similar pattern though.

With reference to what Andy is doing, i really need to find out how cack the existing 225 inlet plenum is? It's of a small bore, but not far dissimilar in diameter to the original boost circuit and turbo outlet. Is it worse that the 172/182 inlet? I'm thinking of making up a new inlet manifold if proven there could be of a good benefit. I propose keeping to the same formula as existing but enlarging from 40mm to say 60mm ie an increase in volume. I haven't really looked into the calculations needed to make the manifold work optimum for this engine so some info would be greatly received.

[i l k e r]

Yes they are different matey. Exhaust is a similar pattern though.

With reference to what Andy is doing, i really need to find out how cack the existing 225 inlet plenum is? It's of a small bore, but not far dissimilar in diameter to the original boost circuit and turbo outlet. Is it worse that the 172/182 inlet? I'm thinking of making up a new inlet manifold if proven there could be of a good benefit. I propose keeping to the same formula as existing but enlarging from 40mm to say 60mm ie an increase in volume. I haven't really looked into the calculations needed to make the manifold work optimum for this engine so some info would be greatly received.

I'm in the same boat really.

O.E 225 inlet definitely looks small in size but bear in mind that it maybe due to small sized ports/valves of the 225 cylinder head.

it's a well known fact that bigger ports are not always the way forward in chase of power. You might increase the overall diameter of the boost circuit but what of the flow? There is no point increasing the bore of the circuit if it is not going make a difference to the amount of air going through it at a given time.
imho without flow tests and some sort of calculations, it's not easy to guess what is better or not.

[Matt Cole]

I'm in the same boat really.

O.E 225 inlet definitely looks small in size but bear in mind that it maybe due to small sized ports/valves of the 225 cylinder head.

it's a well known fact that bigger ports are not always the way forward in chase of power. You might increase the overall diameter of the boost circuit but what of the flow? There is no point increasing the bore of the circuit if it is not going make a difference to the amount of air going through it at a given time.
imho without flow tests and some sort of calculations, it's not easy to guess what is better or not.

Ilker, exactly the point i'm making before even thinking of touching it! Are the port sizes smaller on the 225 than the 172/182 heads? I've never looked at them in comparison, so would need this info to start with.

[i l k e r]

Ilker, exactly the point i'm making before even thinking of touching it! Are the port sizes smaller on the 225 than the 172/182 heads? I've never looked at them in comparison, so would need this info to start with.

from what I gather from the pictures, the ports on the 225 head looks somewhat smaller than the F4R and F7R heads.

Let me get some measurements so we all know for sure

[Matt Cole]

Cheers, I guess this is important info.

[Andrew Cooke]

It's been a while since I played, but I had a bit of a go tonight. Pretty much every 16V head I've seen had the combustion chamber opened up to the cylinder bore along it's side. The 172 doesn't, and it looks to me like the wall shrouds the valve. Only thing to do is open it up and see what gives.

Note that I haven't finished, so far I've just carved the wall out to the bore size using the boring head on the lathe, and some manpower. I've cut down 6.5mm 0.1mm a time, one side at a time. I've not smoothed out, so there should be something to find there.

I was torn between starting work in the port, and starting in the combustion chamber, right or wrong I started inside the chamber.

Pics aren't that clear I'm afraid:



The results were better than I expected, so I guess I'm heading in the right direction:

[Matt Cole]

Thats pretty impressive Andy. I guess theres more to come too!

[Andrew Cooke]

Thats pretty impressive Andy. I guess theres more to come too!

At a guess, the same improvement again just from the chamber, but there should be improvements all the way through. Time will tell...

[Adey aka Ewok]

im abit confused, how has taken meat outa the head that doesnt look like its obstructing anything improved flow?

[Andrew Cooke]

im abit confused, how has taken meat outa the head that doesnt look like its obstructing anything improved flow?

sounds to me like you need to look at it for a bit longer

[Adey aka Ewok]

so it is an obstruction then? im asking stupid questions arnt i

[Ashy]

mmmmmmmm that is interesting Andy, I'm glad you're doing all this work before I build my new engine... I can see an F4R head ending up on on of the CNC mills having some work done

Just out of interest, you've removed the material between the inlet and exhaust, why haven't you done the same front and back i.e. between both inlets and both exhaust valves?

[Andrew Cooke]

I was sure that today's little grivel was going to make a similar improvement as yesterdays, after all I'd done very little near the valve, and that machined edge just looked nasty.

I did a rough shaping job and retested the on the bench. It certainly looked like it should be better:


you can see where I cut down to yesterday.



but the flow bench tells a different story, some improvement at lower lift, but it doesn't set the world alight. It's time to move away from the combustion chamber now, I think I'll need to revisit it later, probably with more subtle changes, see how close I can get to this without taking out so much material.

[Adey aka Ewok]

so the first bit you took out, is that a good gain?