Hermholtz, timing, S13 sr20 delicate natural tuning

[Kingtal0n]

I am having 11-15* Of timing during 10PSI of boost at 14.5:1 Air fuel ratio on OEM sr20 redtop with t-25. The peak VE is HIGH %% and at a very low RPM as expected but even with such high air fuels! I have adjusted the peak VE timing to about 11*, the factory map is something like 7* and similar air fuel ratios. With this much timing I can be around 14.0:1 and safe at 12PSI from this T-25. HAS ANYBODY ever done this with the T-28 @14PSI ON AN S13 ENGINE? I am wondering if the peak VE is going to be tooo high due to the oem cams and the incredible intake manifold for mid-range (hermholtz effect) So the fix is... camshafts(?) upgraded to lower the hermholtz carried torque (peak VE) for midrange... but then I am fighting at 7,000 RPM over hot air with a stock manifold this is asking for charge contamination and high exhaust pressure... even if I keep the LSA very wide on the camshafts. better just to hit it with a topmount and cams, I know. maintaining the factory configuration is necessary however, so the quest is either install the T28 @14PSI and keep it lean with cams (and keep a low rev limit 6500-6800 RPM ) *OR* jump to the cookie cutter 2871R and cap it at 18PSI with cams and 7000RPM redline... what was the question?

[6secondS15]

what the hell are you even talking about? everything i read of yours seems to just over complicate things. put the parts on and try it. i had a t28 on an s13 with the wastegate pretty much constantly shut, cranking as much boost as i could get out of the things. never broke, never blew up.

[srs14]

lol i understand what king is saying but it is still over complicating things. i am an engineering major (i think king is too?) and im always thinking about new stuff that i learn and how it applies to stuff im interested in (cars). i guess i need to read more about resonance of the pressure waves lol.

[lok]

why are you running so lean in boost?

[codyace]

7000 rpm rev limit with a 2871?

That's like pulling out half way through a blowjob....


Spin it to 7800 like the rest of us, and dlove it.

PS: Why would 14 psi with a t28 be a bad thing? That's what 90% of 'stock' SR owners do anyway...both FWD and RWD. As long as the fuel is there, and the tuning is half decent, that will last all day long with hiccup or issue.

[Kingtal0n]

Originally Posted by codyace

7000 rpm rev limit with a 2871?

That's like pulling out half way through a blowjob....


Spin it to 7800 like the rest of us, and dlove it.

PS: Why would 14 psi with a t28 be a bad thing? That's what 90% of 'stock' SR owners do anyway...both FWD and RWD. As long as the fuel is there, and the tuning is half decent, that will last all day long with hiccup or issue.

Sup Cody!
The reason I do not rev must past 6500~rpm is because the VE drops too much. The turbo gives up around 6500 boost failing, power dropping, and even 7000 RPM is a struggle for it. Yes If I swap to a turbocharger than can support 7k+ I will be adding cams, rocker stoppers, and revving to the real red, of course I would love to take advantage of the good VE up top.

Still, the intake manifold on the S13 is not conducive to high RPMS. I much prefer the short runner design of the S14 coupled to the cam timing retard they get.
In contrast, I would rather have shitty VE up top and keep the strong mid-range the OEM S13 intake gives me. basically, using what I have will give less top end, but it will be more of a fun car on the street if I dont hit peak numbers.

So I've made up my mind, the T-25 has to go. I think Ill stick a 2871r .64 on the stock exhaust manifold.
also, I will be keeping the OEM Exhaust system with it.
The a true greddy type-S recirculated shall maintain SILENCE.

The idea here is:
Sleeper + good fuel economy + good street response

Sleeper comes from 320~RWHP and Stock exhaust / recirc'd bov
good fuel economy comes from good tuning
good street response comes from MILD cams, Stock intake manifold, stock exhaust manifold, stock exhaust system.

Yes it will choke a bit with that restrictive exhaust, but the stock manifold is not much better so it will only be a 20-30 HP loss in theory.

Tell ya what, When I get it done, Ill remark about it instead of theorizing all day haha

[Kingtal0n]

Originally Posted by lok

why are you running so lean in boost?

Because it can! MY experience has learned me the lesson that rich air fuels are not always necessary. With 7PSI of boost I can make 200~horsepower with a 15:1 air fuel ratio without a hint of knock, flakey pistons, white plugs, it runs clean and strong. With 11-12PSI (T-25 MAX boost @ redline) I am getting away with 14.3:1~ and it seems very safe, I have intentionally increased the temperature of the intake air by putting the vehicle on a dyno with NO fan and doing back to back runs. As expected, hotter air means less power overall, but the curve does not shift, torque does not indicate a problem with combustion, as long as timing is very very conservative. The engine will pull strong through mid-range torque (3000-4500RPM) with that tiny turbo and it wants about 7-10* Of total timing at peak VE.

The engine is very efficient, and seems very happy and snappy.

of course, a 2871r plus 15-18PSI of boost is gonna find me around 12:1 air fuel or less, for safety reasons, and I wont be beating up the air with a shitty knock-off intercooler either, it will want a nice greddy vspl core minimum IMO.

And a bit more timing after peak VE, maybe as much as 14. I always keep S13 intake SR20's below 11* at peak VE (peak torque) because anything more than that usually creates nasty pistin popin problems haha

[Kingtal0n]

Originally Posted by srs14

lol i understand what king is saying but it is still over complicating things. i am an engineering major (i think king is too?) and im always thinking about new stuff that i learn and how it applies to stuff im interested in (cars). i guess i need to read more about resonance of the pressure waves lol.

The long runners of the S13 intake manifold are like the long runners of the Tuned Port Injection system of the (89-92 camaro TPI L98) engines. They allow acoustic "pressure waves" to help increase the VE%(and therefore torque production) at whatever RPM they are tuned to. in the S13's case, its mid-range torque that gets bumped, while sacrificing top end horsepower.

When they made the switch to S14 engines, the VTC allows the cam timing to move. This gives the same effect, bumping low-midrange torque by allowing the intake valve event to occur sooner at lower RPMS. Thats why they got rid of the Long-runner S13 intake- they no longer needed it to bump the low-midrange torque... Instead they are just moving the cam timing to compensate.

The S14 design is therefore superior, it has the best of both worlds, good mid-range cam profile, backed up by a short runner intake and a whole extra cam profile for top-end power.

The acoustics is known as "hermholtz" and every intake manifold experiences some degree, it has negative effects AND positive effects at various RPMS.

Why am I using the S13 intake then? because redtops are cheap, and My favorite engine is an accident redtop with a stock clutch/turbocharger and a side mount. A true virgin OEM JDM engine is priceless, it hasnt been Screwed with. I slap it into a semi-crappy 240sx with stock exhaust plus a real clutch and a PowerFC, and you have yourself a nice little sleeper. Of course, having a real turbo also helps add the WOW effect.

[Kingtal0n]

Originally Posted by 6secondS15

what the hell are you even talking about? everything i read of yours seems to just over complicate things. put the parts on and try it. i had a t28 on an s13 with the wastegate pretty much constantly shut, cranking as much boost as i could get out of the things. never broke, never blew up.

I have tried it. Actually I am posting because I am bored and I love to theorize and gather other peoples opinions. I also love to help discovery when possible. Many times I learn just by making random thoughts/suggestions/theorys and working them out from there with input from across the room so to speak. I value input more than you can imagine, because just about every person has more experience than I do with unimaginable combinations. I found this board a few years ago and I didnt even know what a Skyline was... technically I am still a noob to "nissan". But it doesnt matter, because the math follows the engine... not the manufacturer.

Yes its fun to put parts on an engine and "test them" but I am too cheap/poor/broke to do back to back dyno runs to make comparisons- i would rather create everything on paper, and imagine it running the way I would expect it to, and work out the kinks before I even buy a single part. You dont always get it perfect, but it works alot better for me than buying things and trying them and crossing your fingers... because now that I have some experience, I can draw on that to make my conclusions about engine behaviors overall.

[srs14]

Originally Posted by Kingtal0n

I have tried it. Actually I am posting because I am bored and I love to theorize and gather other peoples opinions. I also love to help discovery when possible. Many times I learn just by making random thoughts/suggestions/theorys and working them out from there with input from across the room so to speak. I value input more than you can imagine, because just about every person has more experience than I do with unimaginable combinations. I found this board a few years ago and I didnt even know what a Skyline was... technically I am still a noob to "nissan". But it doesnt matter, because the math follows the engine... not the manufacturer.

Yes its fun to put parts on an engine and "test them" but I am too cheap/poor/broke to do back to back dyno runs to make comparisons- i would rather create everything on paper, and imagine it running the way I would expect it to, and work out the kinks before I even buy a single part. You dont always get it perfect, but it works alot better for me than buying things and trying them and crossing your fingers... because now that I have some experience, I can draw on that to make my conclusions about engine behaviors overall.

lol i gues i was right by assuming your in Engineering Coarse. i think the same way. time just doesnt allow me to try or completely plot everything out. and im still learning so knowledge is a big factory in making calculation.

[fabiano]

Originally Posted by Kingtal0n

Because it can! MY experience has learned me the lesson that rich air fuels are not always necessary. With 7PSI of boost I can make 200~horsepower with a 15:1 air fuel ratio without a hint of knock, flakey pistons, white plugs, it runs clean and strong. With 11-12PSI (T-25 MAX boost @ redline) I am getting away with 14.3:1~ and it seems very safe, I have intentionally increased the temperature of the intake air by putting the vehicle on a dyno with NO fan and doing back to back runs. As expected, hotter air means less power overall, but the curve does not shift, torque does not indicate a problem with combustion, as long as timing is very very conservative. The engine will pull strong through mid-range torque (3000-4500RPM) with that tiny turbo and it wants about 7-10* Of total timing at peak VE.

The engine is very efficient, and seems very happy and snappy.

of course, a 2871r plus 15-18PSI of boost is gonna find me around 12:1 air fuel or less, for safety reasons, and I wont be beating up the air with a shitty knock-off intercooler either, it will want a nice greddy vspl core minimum IMO.

And a bit more timing after peak VE, maybe as much as 14. I always keep S13 intake SR20's below 11* at peak VE (peak torque) because anything more than that usually creates nasty pistin popin problems haha

Interesting that its works well at this afr, never tried it. But you would get more power from an afr of 13.5:1 the mixture will burne faster and you should also be able to add a bit of timing.

[Martin XAT]

running that kind of afr just is a complete loss of power.. I idle a car at 15-16 AFR not run boost through it . Since I've had a dyno at my disposal for a good while I got this exact idea in my head a long time ago and tried all sorts of AFR's vs pulling timing on my car and this is what I learned ... at least SR wise with gas

Anything over 14.5 is just not enough gas to do damage.. and you start to loose a lot of power vs running traditional AFR's .. IIRC I think I saw upwards of 30 rwhp loss that lean at about 10 psi on a T25..

Anything in the middle 12.5-14.5 is where you are battling EGT's vs timing vs AFR, and sometimes you just can't come to a happy medium because either you have detonation or you are running EGT's too hot, you pull timing because of detonation.. but you then you run EGT's too high ... and well its a seesaw

I honestly base all my tunes (Enthalpy) on cylinder pressure.. (aka torque - boost pressure) I have found that on a clean running motor 12.5 is more than acceptable up to about the motor's cc displacement / 10 in terms of torque produced.. I linearlly scale it down to 12.0 AFR by about 220 ft lbs.. After that, there is just no point in trying to battle high AFR's with pulled timing, you end up loosing more than you can make by running closer low 12s AFR wise.

I know that the job of many engineers is to invent / reinvent something for the better and try new approaches to traditional methods, but this one's been beat dead.

[Kingtal0n]

Originally Posted by Martin XAT

running that kind of afr just is a complete loss of power.. I idle a car at 15-16 AFR not run boost through it . Since I've had a dyno at my disposal for a good while I got this exact idea in my head a long time ago and tried all sorts of AFR's vs pulling timing on my car and this is what I learned ... at least SR wise with gas

Anything over 14.5 is just not enough gas to do damage.. and you start to loose a lot of power vs running traditional AFR's .. IIRC I think I saw upwards of 30 rwhp loss that lean at about 10 psi on a T25..

Anything in the middle 12.5-14.5 is where you are battling EGT's vs timing vs AFR, and sometimes you just can't come to a happy medium because either you have detonation or you are running EGT's too hot, you pull timing because of detonation.. but you then you run EGT's too high ... and well its a seesaw

I honestly base all my tunes (Enthalpy) on cylinder pressure.. (aka torque - boost pressure) I have found that on a clean running motor 12.5 is more than acceptable up to about the motor's cc displacement / 10 in terms of torque produced.. I linearlly scale it down to 12.0 AFR by about 220 ft lbs.. After that, there is just no point in trying to battle high AFR's with pulled timing, you end up loosing more than you can make by running closer low 12s AFR wise.

I know that the job of many engineers is to invent / reinvent something for the better and try new approaches to traditional methods, but this one's been beat dead.

makes sense, ive been screwing with it blind, no dyno. Remember I am using a T-25 and 7-12psi... I am not fighting to add timing, I am just giving it what it wants. when I had it dialed at 12:1 with anywhere from 15-18* I was getting knock. I pulled it back to 8* around peak torque and my logs have been pristine... slowly I pulled out the fuel bit by bit... they say leaner is meaner... I have been getting best overall results with about 13.5:1 air fuel, scaling the timing from 8-17* as the rpms rise past peak torque

But as you say, only a dyno will tell if I am missing something. I suppose I had better schedule this, and actually figure out what it wants EXACTLY. But first I need a boost controller lol

and i dont have an egt gauge. my idea of egt is get out quickly and see if the manifold is glowing or not XD

[codyace]

Originally Posted by Kingtal0n

So I've made up my mind, the T-25 has to go. I think Ill stick a 2871r .64 on the stock exhaust manifold.
also, I will be keeping the OEM Exhaust system with it.
The a true greddy type-S recirculated shall maintain SILENCE.

The idea here is:
Sleeper + good fuel economy + good street response

Sleeper comes from 320~RWHP and Stock exhaust / recirc'd bov
good fuel economy comes from good tuning
good street response comes from MILD cams, Stock intake manifold, stock exhaust manifold, stock exhaust system.

Yes it will choke a bit with that restrictive exhaust, but the stock manifold is not much better so it will only be a 20-30 HP loss in theory.

Tell ya what, When I get it done, Ill remark about it instead of theorizing all day haha

Stock manifold is the way to go hehe. Just extrude hone it

Interesting theory about the stock exhaust....adding a cutout at all for 'fun' days?

[juggernaut]

This is an Australian based setup using the stock s15 motor which will make most 2871R's left wanting when you start examining the area under the curve its got.

Basic specs are T3 .63 3071 ....21 psi by 3600rpm and 285rwkw/382hp peak with approx 255rwhp by 4000rpm / 281rwhp by 4200rpm.

Stock motor. Baby 255 inlet and 260 exhaust cams. Stock intake. Pump fuel. Australian dyno dynamics.

[codyace]

Considering the differences in dyno readings, that's a really nice graph - looks to be eerrrily similar to the powerband of my car, so that's damn cool considering the bigger housings.

[juggernaut]

Remarkably it hits peak hp around 5900 rpm and more or less holds that peak power to 7400/7500 rpm. Obviously torque is dropping from 5900rpm, but not rediculously so - hence the flat power curve over these rpm.

[codyace]

Originally Posted by juggernaut

Remarkably it hits peak hp around 5900 rpm and more or less holds that peak power to 7400/7500 rpm. Obviously torque is dropping from 5900rpm, but not rediculously so - hence the flat power curve over these rpm.

Sounds veeeeeeeeery much like how my car runs. I love a good solid powerband. Here is my car:

[badhairdave]

wtf happened there!

I was happily reading about afr vs timing theory and all of a sudden my dyno sheet appears!

[codyace]

ok back to afr vs timing. nice chart man

[juggernaut]

Originally Posted by badhairdave

wtf happened there!

I was happily reading about afr vs timing theory and all of a sudden my dyno sheet appears!

Hahaha...and that was your first post since joining nearly 2.5 years ago.

[Kingtal0n]

Originally Posted by codyace

Stock manifold is the way to go hehe. Just extrude hone it

Interesting theory about the stock exhaust....adding a cutout at all for 'fun' days?

What I am feeling is

2871r 64 + stock exhaust + cutout

I have a feeling it will tap around 315~horsepower through the oem exhaust

but through a cutout... it should pick up 20-45hp.

If I am being passed... Instead of hitting a "high boost" button I will be grabbing for the "cutout" button.

lol
can you imagine... OMFG YOUR EXHAUST FELL OFF (as the car leaves)

[codyace]

Originally Posted by Kingtal0n

What I am feeling is

2871r 64 + stock exhaust + cutout

I have a feeling it will tap around 315~horsepower through the oem exhaust

but through a cutout... it should pick up 20-45hp.

If I am being passed... Instead of hitting a "high boost" button I will be grabbing for the "cutout" button.

lol
can you imagine... OMFG YOUR EXHAUST FELL OFF (as the car leaves)

It will certainly be interesting to see how stock exhaust effects total torque produced...I mean it would be an excellent sleeper though with such a setup.

But yes, I know all about the fun of a cutout on a sleeper car. Ran one on my turbo altima at the very end of my ownership

[StockSC300]

Martin XAT know's his ********, I've seen alot of his work from both XAT and Zfever. I was talking with a partner of mine about maybe getting my v8 tuned once its on boost, and the only name that came to mind was Martin. this is also because we live in the greater Tampa Bay area.

In most race applications the helmholtz tuning is focused right before redline. This is done for a few reasons.
One is so the motor is constantly approching peak volumetric efficency. this gives in most cases a smoother more linear curve approaching redline.
Second as HP is a function of torque/time bringing the max torque closer to highest RPM gives you more peak power.

With that being said, area under the curve is sometimes a little bit less. but how many times on a race vehicle are you part-throttling the car other than in the middle of the turns?????

SR20's are street motors, intake and exhaust tuning was done with area under the curve in mind. they want the car to be fun yet drivable. like most street turbo applications helmholtz tuning is still extremely important!!

coming from a manufactures perspective, they have a limited budget for certain design goals, also they are limited to how much HP they want this car to produce. Because you never want to out produce your flagship vehicle(skyline). So they aim'd for a lower number <200hp and picked the turbo accordingly.

Helmholtz on the SR is focused more towards the middle of the motor, so getting into the boost is easier. Once the car is in boost the VE is then sacirficed(spelling) so that the boost can carry the numbers through the rest of the RPM band. Alot of manufactures design this way. one example is the NA vs TT 2JZ intake manifold design.

I recently picked up another book on turbocharging, and found that intake and exhaust tuning is still extremely important on boosted vehicles. some McLaren exhaust manifold designs are really simular to NA designs but focused into collection right at the turbine inlet.

if you want a better example of hemholtz type design work done on SR's, look at a Full Race top mount T3 manifold. it should give you a good example of how runner length tuning can help you in hitting HP goals.

also Greddy intake manifolds for SR's have alot shorter intake runners, this is done to translate where the Helmholtz effect happens, they are trying to move the peak VE towards the redline like I was talking about in the first part of this reply.

[Kingtal0n]

Originally Posted by StockSC300

Martin XAT know's his ********, I've seen alot of his work from both XAT and Zfever. I was talking with a partner of mine about maybe getting my v8 tuned once its on boost, and the only name that came to mind was Martin. this is also because we live in the greater Tampa Bay area.

In most race applications the helmholtz tuning is focused right before redline. This is done for a few reasons.
One is so the motor is constantly approching peak volumetric efficency. this gives in most cases a smoother more linear curve approaching redline.
Second as HP is a function of torque/time bringing the max torque closer to highest RPM gives you more peak power.

With that being said, area under the curve is sometimes a little bit less. but how many times on a race vehicle are you part-throttling the car other than in the middle of the turns?????

SR20's are street motors, intake and exhaust tuning was done with area under the curve in mind. they want the car to be fun yet drivable. like most street turbo applications helmholtz tuning is still extremely important!!

coming from a manufactures perspective, they have a limited budget for certain design goals, also they are limited to how much HP they want this car to produce. Because you never want to out produce your flagship vehicle(skyline). So they aim'd for a lower number <200hp and picked the turbo accordingly.

Helmholtz on the SR is focused more towards the middle of the motor, so getting into the boost is easier. Once the car is in boost the VE is then sacirficed(spelling) so that the boost can carry the numbers through the rest of the RPM band. Alot of manufactures design this way. one example is the NA vs TT 2JZ intake manifold design.

I recently picked up another book on turbocharging, and found that intake and exhaust tuning is still extremely important on boosted vehicles. some McLaren exhaust manifold designs are really simular to NA designs but focused into collection right at the turbine inlet.

if you want a better example of hemholtz type design work done on SR's, look at a Full Race top mount T3 manifold. it should give you a good example of how runner length tuning can help you in hitting HP goals.

also Greddy intake manifolds for SR's have alot shorter intake runners, this is done to translate where the Helmholtz effect happens, they are trying to move the peak VE towards the redline like I was talking about in the first part of this reply.

summary:
1. n/a motors are boosted except that the pressure within is about the same as the pressure without so it feels like n/a
2. race engines need hermholtz assisting in their powerbands.
3. non-race engines need hermholtz assisting in their powerbands.

[Enthalpy]

Originally Posted by Kingtal0n

summary:
1. n/a motors are boosted except that the pressure within is about the same as the pressure without so it feels like n/a
2. race engines need hermholtz assisting in their powerbands.
3. non-race engines need hermholtz assisting in their powerbands.

ONLY a post like this could bring me out of retirement...

its heLmholtz not hermholtz

Hermann Ludwig Ferdinand von Helmholtz

Jesus freaking christ...go on a whole rant about a topic and you cant get the freaking name right...

[Kingtal0n]

Originally Posted by Enthalpy

ONLY a post like this could bring me out of retirement...

its heLmholtz not hermholtz

Hermann Ludwig Ferdinand von Helmholtz

Jesus freaking christ...go on a whole rant about a topic and you cant get the freaking name right...

True that enthalpy... god knows if only I googled "hermholtz" i would have noticed !!

I still say "enantiomer" like "entamiomer"
and I say "diastereomer" like "diatimer"

If we call "cheese" as "apples" but we rant about the cheese anyways...

[gsracer]

seriously scott hasnt posted since june of 2008, good to see your still alive.

from my thread in 2004, 2871 r stock motor, 3 inch exhaust, intercooler , injectors , ecu stock everything else
19 psi

[Kingtal0n]

Originally Posted by gsracer

seriously scott hasnt posted since june of 2008, good to see your still alive.

from my thread in 2004, 2871 r stock motor, 3 inch exhaust, intercooler , injectors , ecu stock everything else
19 psi

iirc thats the engine that lost a piston ring on enthalpy's dyno while he was tuning right? Injector failure? Damn those red tops!
Im about to put a 2871 on a stock redtop myself... sigh