Going To Play With Inlet Tract Length

[Robsbc 0 1 Cars]

i'll set the wife another 'Challenge Aneka' then.... Sounds ideal I'll cut up some existing trumpets so I have somehting to attach the PVC pipe to, then start off long and test various lengths cutting off a few CMs at a time..

 

I assume a test like performing 50-70 runs in 4th, 3 times in a row and taking the average over same piece of road would be a suitable way to test the effects on power ?

 

Sure you want to be testing the car before you had a remap on the new induction length? Your AFR is going to be out

[veloce200 3]

Sean

 

what is your current induction length from trumpet to valve?

what is your current max rpm?

what does your rpm drop down to after shifting in each gear at the redline eg 8000 rpm 1st 6500rpm 2nd?

 

you must consider the induction length of intake together with exhaust. You say that when you do trackdays you often short shift and ride the torque. If you intend to make a lazy torque monster you are going the right way. If you want to compete in sprints on circuit I'd argue you're going the wrong way. If you consider variable inlet systems like TVIS and Alfa Twin Spark you will note they shorten the length as the revs rise.

 

Also TT205 never actually confirmed the results of his experiment. 20lb ft sounds great - but where?

 

also I very much doubt the 50-70runs on the road will do anything more than make it quicker on the road and slower on the track. For sure torque wins races but if you never drop below 5000rpm on track it won't make it any quicker if the gains are below this.

[smckeown 1]

i'll look at what gear best matches wmy current torque range to see what is the best speeds to take comparable results over. From what I have read using the same wide rev band range over and over makes for a good comparison. Maybe 50-70 is too short, i'll look at it again tonight

[veloce200 3]

From what I have read using the same wide rev band range over and over makes for a good comparison. Maybe 50-70 is too short, i'll look at it again tonight

 

you are right and you can tune an engine roughly like that but it's not easy and attracts attention! I remember doing a sprint a brands once - nipped out for 30 mins and came back with 8hp using the Emerald and AP22! I was on the right track to - leaning it out - it was way to rich when I finally RR'd it.

[jacobs53 0]

we usea program at university, which allows us to determine the optimum induction and exhaust port length and size. Aparenetly the 1905cc mi16 should make 215.3bhp maximum @ 7500rpm when the cylinder head is fully worked, and manifolds all correct

 

For me to do this I need

 

*the timing figures of your camshaft, inlet and exhaust (need to know how its measured aswell, at seat or at 1mm of lift etc..)

*port size in length and dia of both inlet and exhaust

*valve seat internal and external dia.

*valve throat size

*max engine speed

*cubic capacity

 

If you take the engine that maxie built up, which produced 216bhp that was near enough on the limit of NA performance.

 

lee

[veloce200 3]

we usea program at university, which allows us to determine the optimum induction and exhaust port length and size. Aparenetly the 1905cc mi16 should make 215.3bhp maximum @ 7500rpm when the cylinder head is fully worked, and manifolds all correct

 

For me to do this I need

 

*the timing figures of your camshaft, inlet and exhaust (need to know how its measured aswell, at seat or at 1mm of lift etc..)

*port size in length and dia of both inlet and exhaust

*valve seat internal and external dia.

*valve throat size

*max engine speed

*cubic capacity

 

If you take the engine that maxie built up, which produced 216bhp that was near enough on the limit of NA performance.

 

lee

 

can you work out the optimum exhaust manifold too?

[smckeown 1]

we usea program at university, which allows us to determine the optimum induction and exhaust port length and size. Aparenetly the 1905cc mi16 should make 215.3bhp maximum @ 7500rpm when the cylinder head is fully worked, and manifolds all correct

 

For me to do this I need

 

*the timing figures of your camshaft, inlet and exhaust (need to know how its measured aswell, at seat or at 1mm of lift etc..)

*port size in length and dia of both inlet and exhaust

*valve seat internal and external dia.

*valve throat size

*max engine speed

*cubic capacity

 

If you take the engine that maxie built up, which produced 216bhp that was near enough on the limit of NA performance.

 

lee

 

I dont have all that information. Maxi's isn't 1905cc

[jacobs53 0]

yeap, program is called 4 stroke head. Its used by top race teams including Ilmor racing (mercedes F1 engines)

 

I can also determine if the camshaft your using is adequate the power your looking for when I have all the information.

 

lee

[jacobs53 0]

I know maxi's is 2.05cc and the limit was 223bhp. So bloody close on the performance limit, must say well done!

 

Shame you don't have that information, there is a good book which will give you a general idea about manifold lengths. Graham Bell 4 stroke performance tuning

 

lee

Edited October 17, 2006 by jacobs53

[veloce200 3]

fancy copying it and sending it out to 205 drivers then ?

[jacobs53 0]

Unfortantly I don't have the software. And ive had no luck obtaining it neither.

 

If you want me to test something pass me the above information and Il relay the results.

 

lee

[B1ack_Mi16 67]

I know maxi's is 2.05cc and the limit was 223bhp. So bloody close on the performance limit, must say well done!

 

How can you know that? Performance limit is more or less set by the heads ability to flow and camshaft profiles. 1.9 BTCC erngines didn't they produce over 300bhp N/A?

 

You did the assumptions with the same camshafts as Maxi's got, or std ones??

 

However using such programs to see differences in the VE when doing changes to inlet-tract lenght and diameter can be useful.

 

I've been doing quite some simulations on my 2.3 litre engine in Engine Analyzer pro.

There you enter flow @different valve lifts and basically every little detail about the engine.

 

Then do simulations with different lenghts and see VE table plots to compare the curves from the different results.

 

It's maybe not a god way to "assume" engine power, but you'll at least see what effect altering some variables will have on power.

[smckeown 1]

Ok I've been studying the links posted by PeterT more, and I was put off by the complexity at first, but they are not that bad.

 

So these are the assumptions i'm making about my current inlet length on the 90mm KMS TBs:

 

Item Length (CMs)

TBs 11.8

Trumpets 9

Head 4 (8cm has been listed as the mi16 lengh, i'm assuming the 8v will be smaller??)

Inlet 7.2

Total 32

 

This is a graph showing the revs at which revs my engine (using my cam as input) should benefit from the reflections (using this as the reference algorithms)

 

 

I have also shown my current inlet length to indicate what increases I need.

 

So from this i can deduce that I am already benefiting from the 10% Reflection 2 at 4000 revs. I have checked the figures in the graph and they seem right to me when i work out the quoted algorithm manually

 

Here I have posted my current torque outline. Are the 3 peaks the 2/3/4th reflections ?

 

 

 

Lastly, the figures from Intake Runner Length Computation by Bowling and Grippo suggest I need much longer runners. Specifically, according to their figures, i'm only benefiting from the 4th Reflection 7% at 5.8k revs. Whereas if I add 10cm more (feasible) the I'll benefit from the last 2 reflections and lower down the range

 

[jacobs53 0]

The program calculates max BHP by using the BMEP value, cylinder volume and engine speed.

 

For example the ideal situation on a NA engine is 100% VE, which in theory is nearly impossible (can be up to 98% in some cases) unless you have a larger atmospheric pressure (more than 14.7psi) so a 1998cc engine which recieves 100% VE multiplied by the BMEP figure will display the maximum output for a engine size relative to each cylinder recieving 100% of VE.

 

So what I have learnt so far is that I can use certian cam profiles, and then obtain manifold lengths put these findings into ricardo wave simulate the engine running to obtain a power output. The camshaft can be modified in any way or form, but some of the best cam profiles are dynamically not suitable, due to excessive wear to the followers or valve bounch occuring.

 

Im still new to the program but im hoping to develop a set of cams for the EW10 engine, which should break the 200bhp barrier, obvesiously with the manifolds to match.

 

lee

[veloce200 3]

For example the ideal situation on a NA engine is 100% VE, which in theory is nearly impossible (can be up to 98% in some cases) unless you have a larger atmospheric pressure

 

it's not impossible at all. By configuring exhaust and inlet to work together (all this talk of inlet is missing the point - exhaust tuning with inlet should be the thread) you can acheive more than 100% VE - 110% is possible...that is the whole point of pressure waves.

[Rippthrough 98]

it's not impossible at all. By configuring exhaust and inlet to work together (all this talk of inlet is missing the point - exhaust tuning with inlet should be the thread) you can acheive more than 100% VE - 110% is possible...that is the whole point of pressure waves.

Yup, the latst M5 hits 108% at some points IIRC

[Sandy 189]

Engine modelling software is not definitive, there are so many variables at work that you cannot accurately predict what set up will work best. The only reliable way to establish the best set up (for the kind of curve you want) is experimentation, this software is at best IMO, a vague estimate and curiosity only. There are patterns to the way engines perform of course, but the tiniest variations on port work, valve seat geometry, piston acceleration, chamber work, cam profiles and other influences can make vast differences to the power curve. A friend of mine that is currently developing a large capacity Duratec, has just spent alot of Dyno time on different cam profiles and tract length, he was working around 340-360mm length because that's were he would have got the best results with similar other 16v engines at that capacity and those profiles, but finally settled on 70mm less with pretty much more power everywhere! A situation that is unique to that engine, his smaller capacity Duratecs aren't the same. Take nothing for granted!

[B1ack_Mi16 67]

it's not impossible at all. By configuring exhaust and inlet to work together (all this talk of inlet is missing the point - exhaust tuning with inlet should be the thread) you can acheive more than 100% VE - 110% is possible...that is the whole point of pressure waves.

 

Exactly, engine analyzer recons actually about 118% VE @ max on the simulations I've done on my engine!

Not that I know if it's realistic, but at least it's a sign of that it's no problem getting more than 100% VE on a N/A engine. The program is suggesting I'm getting around 250bhp with my current spec, which is actually what I'm hoping for, but guess it'll be like 240 - 250 somewhere.

 

I also had a course @UNI about combustion engines, and there they also said that VE = 100 was maximum, they can't really be into anything else than large diesel engines for ships

[B1ack_Mi16 67]

Engine modelling software is not definitive, there are so many variables at work that you cannot accurately predict what set up will work best. The only reliable way to establish the best set up (for the kind of curve you want) is experimentation, this software is at best IMO, a vague estimate and curiosity only. There are patterns to the way engines perform of course, but the tiniest variations on port work, valve seat geometry, piston acceleration, chamber work, cam profiles and other influences can make vast differences to the power curve. A friend of mine that is currently developing a large capacity Duratec, has just spent alot of Dyno time on different cam profiles and tract length, he was working around 340-360mm length because that's were he would have got the best results with similar other 16v engines at that capacity and those profiles, but finally settled on 70mm less with pretty much more power everywhere! A situation that is unique to that engine, his smaller capacity Duratecs aren't the same. Take nothing for granted!

 

I really see your point, anyway it might give a ok indication on single modifications to run simulations with different inlet tract lengths. But of course the simulations will never be any better than the data you put into the program.

[smckeown 1]

I hear you guys, so it's experiment experiment experiment

 

So is it the case this experimentation should't be done on the road as it may result in the car running lean ?

 

If I want to play, should I get an AFR display ? And if I saw a lean mixture i would back off ? or try and enrich the mixture at that RPM ? Then once I think i've found the right length, get the trumpets mad eup properly and get the map fine tuned at the RR ??

 

The benefit of the KMS lambda display ois that it can also display 2 other aux inputs, so I could dump my existing (and probably inaccurate) oil pressure and oil temp gauges. Then I might as well junt the inaccurate speedo also for a cheap bike speedo, and go thw whole hog and get a cheap tacho too and end up with a cheap(ish) custom dash

[Sandy 189]

You can use the AFR as a good guide to where you're picking up VE with your alterations, as it will lean off as VE improves generally, it's arguably a better way to analyse alterations than a rolling road (not a dyno though), because the ambients can be more consistent on the road.

[smckeown 1]

cheers sandy, i'll get the KMS lambda controller and display on order. Will be interesting to se eif the controller actually makes any recommendations also if i'm playing with the induction side.

[Sandy 189]

Just to give you a fuller picture, once you've settled the set up and corrected the fuelling, a trip to the rollers to optimise the ignition is a good idea, otherwise the improvements might not translate into more power, if combustion is too early or too late.

[Rippthrough 98]

Don't forget that the increased/decreased momentum of the gas in the inlet due to the length of the length of the runners will have an effect too. Probably why the two calculators give different results - trying to compensate for it in different ways.

 

-Phillip

[Mandic 0]

Anyone have any more info about those resonances?

 

People cut mi16 mani and get good top rpm range power gains but according to that calculator gains shloud be bigger if using longer mani due to 2nd harmonic.

 

What about You Sean? Any progress?

 

Cheers

 

Ziga