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Bigger Throttle Body Nonsense (By Chip Wizards) stock v Bigger throttle

924Srr27l

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Some of the explanations in the piece (below) in regard to how an Engine pulses are also very relevant to the Bosch AFM, which has a Myth that does the rounds
that's it's restrictive and in some sense as this explanation illustrates it's similar to when some people think a bigger butterfly throttle body and / or more air is required to give your engine more Power. Some of this also features with the various forms of taking off the AFM and using aftermarket systems and electronics to do the same job (even though they are often fitted from the declarations they are better but can often be a lot worse!) as electronics made and developed even in the 80's by Bosch are regarded as very high pieces of Electronically high cost to develop kit.

The principles also work the same for the Exhaust gas Pulses and in regard to the size of the tubing Bore, Gases stay hotter and exit faster in a smaller bore
than a larger one, this I believe plays a big part to why my motor produced more torque and power (and lower down) because not only does it have a 30+ year old AFM, but the exhaust Tubing is 2" OD, Not ID hence the stainless thinwall 1.2mm tubing gives an actual ID of 48.4mm which is almost
5mm smaller than a 2.25" Stock system which also has 2-3 restricted silencers in the system.

Forced induction has far more issues with getting rid of all the gases and needs a bigger bore to physically remove them quickly because the mixture and burn has been forced in, and hence needs forcing out ready for the next cycle / pulses howver the same principles apply , go too big and it'll respond less and produce less power.
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Bigger Throttle Body Nonsense

I love my dyno, it’s great.
It doesn’t suffer from any placebo effects, it doesn’t read biased rubbish on the internet, it doesn’t try to sell you anything or try to convince itself that its most recent purchase was not a total waste of money and it doesn’t flatter with "suits you, Sir” lies; it just measures what is being produced and shows it, warts an’ all.
So, now that’s out of the way, let’s look a little bit at HOW engines breathe, since that’s what induction changes seemingly set out set out to improve…..
Suck, squeeze, bang, blow right? Yes of course, mostly.

However, imagine that a given engine has a cylinder capacity of say, 3000cc, so each revolution it would DISPLACE 1500cc (1.5 litres), and that it’s running at 6000 rpm; that’s 100 revs per second so 50 CYCLES per second and thus, 150 litres per second @ 100% Volumetric Efficiency (VE). Think about that, a hundred and fifty litres per SECOND.
Well, given how fast that is all happening the VE isn’t going to be anything like 100%, is it, because there’s so little time to fill and empty the cylinders, right?
All the little restrictions along the way; air filter, trunking, intake silencer, throttle body, plenum chamber, intake runners, ports in the cylinder head, past the valves (which are closed for more than half of the time) and that’s just to get TO the cylinder, after all that it’s still got to get out….
SO…. what would you realistically expect the VE to be in such circumstances? Well, if you were to put a huge vacuum cleaner sucking at an unrestricted rate of 150 l/s (saving the piston’s uppy-downy motions from doing the job) pulling air through to the cylinders you’d get, perhaps 75% of the potential unrestricted flow. In that case there’s 25% of the potential flow lost to the restrictions.

You’re never going to get ZERO restriction because there’s far too much other necessary stuff in the engine and engine bay to fit filter, trunking, manifold and ports of sufficient proportions to have zero restriction.
A modern engine is pretty good out of the box and you wouldn’t ever expect as much as a 5% improvement in flow without drastic changes, and those very same drastic changes would likely make things worse in other ways. So, best ways up you might see 78 or 79% of the potential flow.
How come then, a typical modern high-performance road car engine has a VE of as much as 120%? Yes, a 3 litre engine would breathe as much as 3600cc in two revolutions!

With its silly uppy-downy pistons, pulling air past valves that are only open for typically 36% of the time, through ports that often have rough surfaces and uneven profiles, through often convoluted trunking and in from the outside world through a filter that only has open areas of a few microns. It cannot possibly be, surely? That’s over 50% more than the possible flow when the valves are only open for 36% of the time and the piston is only on the induction stroke for half of a revolution. "Get the ducking stool ready people, something isn’t right…..”
Well it can and it does, using PRESSURE WAVES. Tuning pressure waves is what it’s all about. Camshafts, exhausts, intake systems SHOULD all work absolutely together to harness the highs and lows of the pressure waves to best effect; so effective in fact that it amounts to a very significant supercharging effect.
Flow plays a very low second fiddle to pressure waves when it comes to tuning, because the difference that a loss of wave amplitude makes is far greater than the potential flow ‘increase’ from having a larger diameter and guess what? When the diameter of a pipe increases, the amplitude of the waves within it reduce because the molecule compression occurs over a greater area (the surface area, if you will, of the pipe section), so while the static flow may be imagined to be greater, the dynamic flow is actually considerably less.

For example, just look at a GT or F3 airbox - the airbox is huge to harness the pressure waves but the inlet FLOW is through a tiny little inlet restrictor, and despite this the engines still make PLENTY of power.
A flat six engine (all sixes actually for a specific reason that we don’t need to entertain here) is particularly well suited to harnessing the pressure waves that travel back and forth into, as well as across, the manifold if allowed to. They can make a huge difference to the VE at some engine speeds. This is why the (not stupid) design engineers at Porsche have gone to such great lengths to make best use of the pressure waves by employing various flaps in the system to either block or allow passage of pressure waves within the system.

When developing their engines manufacturers will do many, many hours of simulation work. After that they will make many test pieces, probably at least twenty different head casting designs, fifty camshaft profiles, piston crown designs, valve head shapes, compression ratios, manifold designs, you name it. At each engine test, a zillion sensors and probes are mounted all over the engine measuring everything that can be measured.
DO YOU NOT THINK THAT AT SOME POINT IN ALL THAT IT WOULD HAVE BECOME APPARENT TO THEM THAT IT NEEDED A BIGGER THROTTLE BODY?
No, of course not, they’re all stupid those Germans, right?
It takes Fred in his shed with probably zero engine design expertise, to think "Gad Daim, I can fit me a bigger throddle on there an’ life will be reeeeeal gewd….”
If only things were that simple…..
In the vast majority of cases BIGGER THROTTLE INTAKES DON’T WORK so save your money.
In every single Porsche case that I have EVER had on the dyno, NO bigger intake has made an improvement, and almost ALL has made less area under the curve than stock.
When a vendor selling parts says "There’s a 25 bhp difference with this Big-Boy Carlos Fandango intake Sonny Jim” just consider whether he means UP or DOWN!!!!!!

See Image for Dyno results stock v Bigger throttle fitted

(Chipwizards - Wayne Schofield)
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R


 
Thank you very much for sharing this. Any more similar insights into the truths of tuning our cars would be most welcome.
 
Paul 290T said:
Thank you very much for sharing this. Any more similar insights into the truths of tuning our cars would be most welcome.



Hi Paul

Check out Chip Wizards on Facebook...like the page and you'll get the updates. IIRC, Wayne posted this on FB a few weeks back.

Pete
 
The only posts I recall relating to running a larger throttle body on a 944, are on 944 3.0 16v turbo engines. So Chip Wizards post about the 996/Cayman don't have much relevance on this board.
 
blade7 said:
The only posts I recall relating to running a larger throttle body on a 944, are on 944 3.0 16v turbo engines. So Chip Wizards post about the 996/Cayman don't have much relevance on this board.


It's relevant to ANY Engine ! It's point is a description and summary of how an engine works and what doesn't work in this case is fitting a larger bore throttle body.

There are plenty of Normally aspirated 24's 44's an 68's on this board, besides it also applies to forced induction.

Wayne's point is (as he humorously suggests) their are many cases and products that claim to Increase horsepower and in this example there are bored out OE throttle bodies available (ebay) and aftermarket stuff from china on the market.


In light of his descriptions in regarding to Pulses etc..I'm also keen to get across and correct any doubters who think the Bosch AFM is some restrictive device
(as there's been a fair amount of this on numerous forums). It actually helps the pulses, hence why Wayne referred to other modern engines using flaps to open and close air volumes. The RS Ford Focus 2.0 Zetec used a variable Inlet system, as did the 1.6 4age Toyota (Bda replica) + many more..

Pulses and volumetric calculations all very important and worked out by people that know how to, and not others that want to sell products or they think some
add on will make their car faster.

Can you imagine how many components and claims Wayne has seen over the last 3+ decades, the beauty is he's an engineer (engine tuner) and does not have any component or mechanical tuning work to sell, but from all his knowledge and experience he understands what works and what's just hyped up chatter....and doesn't mind telling people about this free of charge!


R

 
Two of the biggest Components that often claim to increase performance but Fail are air filters and Exhausts.........

Both are usually bigger volumes (Big bore back box) and Large (Cone filters) to Upset the engines air pump Pulses...
Both make much more noise, and 99% of people who have fitted them swear the car is quicker !!


All relevant to all car's & engines and all Porsche transaxles N/A & Blown...
R
 
On the subject of the standard AFM that Rogers brought up. Interestingly enough my car is still at Wayne’s but when I brought it to him I was asking questions on my set up and what he recommends Whats the best components ect.

after telling him all my mods to date ,he asked me if I had a standard bosch AFM or an aftermarket maff with wire ect? ....I told him unfortunately it’s next on my list but for now I’m still running the big standard AFM ( all Be it re calibrated by John Mitchell ,......and to my supprise he said thank god!

After discussing it , he says you get the best tune with the AFM and the talk of it being restrictive and only measuring 3 opening angles isn’t totally correct, and he rates the standard AFM above any aftermarket maff ! All to do with the back air preasure waves which will fly backwards past the measuring wire and give false readings ect ,....whilst the barn door will shut and stop measuring on let off after hard excelleration.

Dont quote me on that 100% but you get the idea.

needless to say I was o er the moon and if I had a aftermarket turbo (my next treat) I would have a seriously powerful 951. For now I’m happy with what ever it comes out at as long as I have longetivity and can use the power and enjoy my car withought any danger of Over heating components ect. ??

looking forward to getting her back!
 
Dan944t said:
After discussing it , he says you get the best tune with the AFM and the talk of it being restrictive and only measuring 3 opening angles isn’t totally correct, and he rates the standard AFM above any aftermarket maff ! All to do with the back air preasure waves which will fly backwards past the measuring wire and give false readings ect ,....whilst the barn door will shut and stop measuring on let off after hard excelleration.


What does he say about MAP based systems? And perhaps you should read what Jon Mitchell has to say on his website about the AFM on high output 944 turbo engines...
 
I will ask when I pick my car up, if there’s something specific you’d like me to ask just let me know, and I will ??

john is very knowledgable mate yes and I think I must have read that years ago among with maybe most things his ever wrote about , which is why I spent over £4,000 with him.

are You refering to a 951 can’t make more than 320 bhp with a standard restrictive AFM? It’s been a long time since I read it
 
Dan944t said:
I will ask when I pick my car up, if there’s something specific you’d like me to ask just let me know, and I will ??

john is very knowledgable mate yes and I think I must have read that years ago among with maybe most things his ever wrote about , which is why I spent over £4,000 with him.

are You refering to a 951 can’t make more than 320 bhp with a standard restrictive AFM? It’s been a long time since I read it


On his website Jon says 340 bhp. So the majority of owners will be fine with a properly working AFM. That doesn't mean a AFM is better than all modern standalone systems, that make use of a lambda sensor, and can be tweaked from a lap top in seconds.
 
340 is pretty good power!

I am very intrigued to find out what mine makes being that I’m running a standard 220 turbo all be it freshly rebuilt but still standard size., and standard AFM.

what power do you think mine will achieve?

Also what power is yours pushing Tony? And what mods have you added from standard?
 
Well some years ago three of us spent a very long, and less than entertaining, day oop North when Wayne (when he finally turned up) demonstrated his complete inability to map the Link MAP system on three different cars. I have said elsewhere that it was a git to work with but I ultimately achieved better results running up and down a local dual carriageway. And I didn't set fire to my car while doing it.

I have every confidence that in many peoples eye's Wayne is a mapping Demi God, and his words are beyond reproach, but we are all human.
 
Dan944t said:
340 is pretty good power!

I am very intrigued to find out what mine makes being that I’m running a standard 220 turbo all be it freshly rebuilt but still standard size., and standard AFM.

what power do you think mine will achieve?

Also what power is yours pushing Tony? And what mods have you added from standard?


Hi, did you not consider a flowed cylinder head and cam ?

Or did you want everything to be all stock and standard ?

did you have the pistons, rods, crank, flywheel etc...balanced?

Lindsey Racing say the stock 952 inlet manifold is not as good (equal flowing) as the N/A because the number 1
inlet runner is longer than the other 3

R

 
924Srr27l said:
Dan944t said:
340 is pretty good power!

I am very intrigued to find out what mine makes being that I’m running a standard 220 turbo all be it freshly rebuilt but still standard size., and standard AFM.

what power do you think mine will achieve?

Also what power is yours pushing Tony? And what mods have you added from standard?


Hi, did you not consider a flowed cylinder head and cam ?

Or did you want everything to be all stock and standard ?

did you have the pistons, rods, crank, flywheel etc...balanced?

Lindsey Racing say the stock 952 inlet manifold is not as good (equal flowing) as the N/A because the number 1
inlet runner is longer than the other 3

R


HI Roger ,

i actually built my engine as a bit of a one off really, bit of a frankinstine.

Ive had my cylinders totally milled off and racing steel liners made and fitted , slightly oversize and thicker walls than standard so they can take big boost. Iasa pistons and rings, custom one off lightweight Conrad’s made for me in millan each 220 grames lighter than stock, lightened flywheel, slightly lightened crank, all balanced along with all my pulleys ect.

crank scraper, I made my own flow bench and desided to port and polish my head espeacially concentrating around the inlet valve bulge making it into a teardrop for hopefully better flow, kept the standard size valves, new cut valve angle job, for hopefully better flow,polished valves, polished bowls and very slightly modified, head inlet ports have a one off swirly stippling for air and fuel mixing ?? done my own manifold hone to make as smooth as possible but swirly.( it was extremely spiky and uneven between chambers)
Took me around 6 hours

Comettic 5 layer stainless head gasket
Standard AFM
38mm Tial dualport wastegate
Stage 2 intercooler
cone filter
manual boost controller
55lb injectors
964 turbo fuel pump
rebuilt turbo
hard boost lines
syntec adjustable fuel preasure reg with gauge
993 recirculating valve
new dizzi cap,rotor, beru spark leads, arridium plugs
LR water way in back of head mod to remove hot air pockets
AFR gauge and sensor
boost gauges
Heat wrapped down pipes and turbo pipes
ceramic coated manifold
sports rear exhuast (hardly any restriction)
quick shift linkage in gearbox ect ect
All being tuned at Wayne’s right now.

I’m sure I’ve missed a few mods but that’s the majority.
everything along with the total engine rebuild done and fitted by myself everything apart from the cylinder work and balancing of components, angled valve seat cut , head skim and polish, which was done by Jon at serdi U.K.
 
Dan944t said:

HI Roger ,

i actually built my engine as a bit of a one off really, bit of a frankinstine.

Ive had my cylinders totally milled off and racing steel liners made and fitted , slightly oversize and thicker walls than standard so they can take big boost. Iasa pistons and rings, custom one off lightweight Conrad’s made for me in millan each 220 grames lighter than stock, lightened flywheel, slightly lightened crank, all balanced along with all my pulleys ect.

crank scraper, I made my own flow bench and desided to port and polish my head espeacially concentrating around the inlet valve bulge making it into a teardrop for hopefully better flow, kept the standard size valves, new cut valve angle job, for hopefully better flow,polished valves, polished bowls and very slightly modified, head inlet ports have a one off swirly stippling for air and fuel mixing ?? done my own manifold hone to make as smooth as possible but swirly.( it was extremely spiky and uneven between chambers)
Took me around 6 hours

Comettic 5 layer stainless head gasket
Standard AFM
38mm Tial dualport wastegate
Stage 2 intercooler
cone filter
manual boost controller
55lb injectors
964 turbo fuel pump
rebuilt turbo
hard boost lines
syntec adjustable fuel preasure reg with gauge
993 recirculating valve
new dizzi cap,rotor, beru spark leads, arridium plugs
LR water way in back of head mod to remove hot air pockets
AFR gauge and sensor
boost gauges
Heat wrapped down pipes and turbo pipes
ceramic coated manifold
sports rear exhuast (hardly any restriction)
quick shift linkage in gearbox ect ect
All being tuned at Wayne’s right now.

I’m sure I’ve missed a few mods but that’s the majority.
everything along with the total engine rebuild done and fitted by myself everything apart from the cylinder work and balancing of components, angled valve seat cut , head skim and polish, which was done by Jon at serdi U.K.



Sounds a great spec, I'll say at least 300bhp, and the low and mid range torque will be good also as Wayne's skills are far more than acheiving a
the biggest top line figure.

R
 
John Sims said:
Well some years ago three of us spent a very long, and less than entertaining, day oop North when Wayne (when he finally turned up) demonstrated his complete inability to map the Link MAP system on three different cars. I have said elsewhere that it was a git to work with but I ultimately achieved better results running up and down a local dual carriageway. And I didn't set fire to my car while doing it.
I have every confidence that in many peoples eye's Wayne is a mapping Demi God, and his words are beyond reproach, but we are all human.



That sounds very feasible John, if by your own admission the Link system was difficult to work on then the results from anyone were never going to be great.
Wayne has many niches of experience not just the Porsche transaxle engines but many others like Peugeot etc.. and he also does a lot of Race cars including the Fully restored Porsche 924 Carerra GTP Le Mans car which I heard the Porsche GB Dealerships had some difficulties getting to run well, but Wayne got the bird sorted.

https://www.porsche.com/u...c/924-gtp-restoration/


R
 

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