My high compression + boost concept

[GasedT18]

Rodger,

you might be interested in this:

http://www.network54.com/Forum/12159...r+supercharger

I'm under no illusion about this and similar 'left field' ideas. I think you are being a bit mischievous throwing it into the thread, a red herring no less??? ;-)

While the sound of trumpets and turbos caught my ear, um eye, the question it seems does come down to matching an appropriate turbo to the engine and engine management - liveliness under low boost being a matter of the intrinsic torque response of the engine and perhaps some degree of ignition advancement that would be tapered off under more demanding conditions. Then of course there is the efficiency of the turbo which at low engine RPM would demand a low inertia/fast spooling set-up. That twin turbos are used, a smaller more responsive one for the low end suggests that some engineers are on the ball.
However, working with higher compressions is fine if one can stay within the safe envelope. Even with careful choice of fuel and tuning under the typical hot environmental conditions we have it may well challenge the average ECU tuners expertise and it may be that under quite a large range of conditions only small levels of boost is achievable and the low end target might seem a bit dismal.

I'd pay attention to detail in the combustion chamber - make sure there were no sharp edges. That some get more out of high compression engines probably owes a lot to the design of the combustion chamber as well as how long it stays clean.

I would want to know that my knock sensor was working and that my ECU (and tuner) could identify ping - an issue which was brought up in another thread in this forum:

http://www.toymods.net/forums/showthread.php?t=16722

Which lead me to this rather interesting thread on another forum:

http://forums.nasioc.com/forums/show...0&page=1&pp=20

I'm not an expert, know nothing about sonics and tuned inlets. The length of the inlet runners even on forced induction does seem to have a role. Here is an example of quite long runners - not to mention long overall intake (second picture from the bottom):

http://www.amworks.com/gallery/fiat19/kuva2.jpg

0-100 km/h 3.9 sec
265 km/h 8100 RPM
top speed 300km/h at 1800m

David

[myne]

I read an article in street machine recently (while bored shitless at work) that stated that one of the v8 drag cars they'd seen had an appropriately sized single turbo that spooled from 0-20psi in .5 of a second. They claimed also that that is better than some superchargers (mine most likely) and that it wasnt a number they'd pulled out of their ass, but a point of data logged by the engine management system.

I think the key to any modern turbo setup is to find someone that knows thier shit, that knows what turbo will get the best response for that engine, and to ensure you get the most up-to-date technology.

Turbo technology is loosely similar to jet turbine technology, and in the last few years, people like boeing have managed to create engines much much larger than the older types, that get far better economy and power. The one I saw in a docco was claiming that this engine they were testing fitted to a 747, that looked nearly 2x the diameter of the stock engines was capable of flying the plane by itself.
The 747 has 4 engines as standard. This more modern engine could have replaced all 4 of them, got more power, and better economy.

Way I figure it, the turbo guys probably pinch a lot of their improvements from projects like that.

[trd3sg]

trd3sg: sounds like a good plan, have you considered mapping it for an ethanol enhanced fuel?

this friend you know, how long he he been running this setup. I will have carefull mapping and I might be doing something very unusual by using a nissan air flow meter.

1J injectors seem to be the go, 380cc and are physically compatable (non VVTi)

I am still building this engine and I can say that it will be in as new condition.

please keep me updated on your progress.

ive been using united 98 for bout 4 months now with the microtech in n/a form and it has been fine so will definitely be using this again post turbo. i occasionally put it on a diet of bp ultimate and some injector cleaner as well just for good measure

the silvertop 20v i was talking about wasnt really a friend, just someone i knew who a friend of mine dyno'd his car - i dont know how long it survived or if its still going but my point was merely that if such a cheap and shoddy setup ran fine on 15psi and made 220fwhp, then a well thought out system with safer tuning of say 12psi and a properly sized turbo would be fine.

if i were you i would steer away from any afm and go for a proper aftermarket ecu using an inbuilt map sensor- at the very least a microtech or haltech and if u have the cash, an autronic\motec

im running with series 5 rx7 13bturbo injectors (550cc) and a bosch 910 fuel pump being primed by my standard in tank pump, with fuel pressures being regulated by a malpassi rising rate regulator - this should supply plenty of juice to the motor for my goals

as for the turbo itself - im using a high flowed t3 with a 0.63 rear and t04d front housing. This should be OK (read only just) for my goals of 10-11psi with the compression ratio i have. You have to remember that the higher compression ratio means higher exhaust pressures which effectively lowers the efficiency of the turbo. On a motor running say 8.5:1 static compression this same turbo would be good for up to 17psi (roughly speaking). Im only using this cos this is a 'cheap' project which im slapping together for bout 2 grand so i dont really wanna go out and spend say 1000 on another turbo seeing as i have 3 spare turbos here at home lol. Ultimately i would like to have run a gt30r or the kkr equivalent (kkr430) with a 0.86 rear but meh ill see how i go with the t3.

for your setup i would be using something like the kkr330 or a garret disco potato gt28rs with .86 rear as well, to give it that added efficiency and reduce any risk of rising intake temps after an hour of driving.

edit: to all those reading above and thought "2 grand my ass" - ill justify it by saying that most expenses had already been covered or i had most things here ready to go. ie i had the fuel pump, regulator, turbo, manifold bends and flanges, microtech and wiring etc etc so most things im paying for are piping, intercooler, exhaust and retune and a new heavy duty clutch plus misc costs like nozzles and gaskets etc oh and an exernal core type engine oil cooler.

good luck mate

[Sam_Q]

my ecu has a built in intenal map because quad throttles are known to cause issues on medium loads off boost due no map signal over partial openings and under boost due to pressue differentials accros the throttle bodies. I want to run an airflow meter to have proper air metering all the time. I personally dont see a problem running one.

[30psi 4agte]

this is the thinking with modern engines from factories...
higher compression, low boost, gives a nicer, more drivable car..
check the calcs for 3000rpm tuning.. you might find the trumpets are a little long..
also, at 3000rpm, the energy is not really there to have a huge difference using harmonics, so it may not be an issue...

good concept, might need to be just a little careful with both tuning and boost with the 10.5:1... start feeding the boost in slowly to see when it starts to detonate..

Im having harmonic issues with my plenum. How do you calc runner length ???

[Rodger]

Ok now I know how much of an increase in power your chasing. So yes I will step out and let the force fed boys refine the set up as you are right it would cost too much to get that increase from an N/A motor.

Thanks Sam_Q.

I continue to read with interest.

Regards

Rodger

[GasedT18]

30psi 4agte

I'm having harmonic issues with my plenum. How do you calc runner length ???

You and others, if you don't already know of it, might want to search for answers on this site:

http://www.eng-tips.com/

Beware - this is an expert site and appears to be intended for engineers, they are not as generous or forgiving as experts on Toymods. From memory there are intake software simulators and other software simulators discusssed on this site.

The last time I looked into tuned intakes my brain melted. There is detail beyond my mathematical ability. I'm not going there. Bill Sherwood has:
"As an example, a 4AGE with fairly big cams which you want to make max power at around 8,000 rpm would need an inlet length of about 10" http://www.billzilla.org/engineintro.htm#Inlet

I didn't know about this:
World's First Continuously Variable Intake Manifold http://67.153.245.114/speawards/2003...kemanifold.htm

And there is this thread http://toymods.net/forums/showthread...=Plenum+design

I am interested in why you think/know you have "harmonic issues" with your plenum? How does it manifest? And is that avatar a pic of your engine?

Cheers

David

[The Last Streetfighter]

I've also started looking at stock CR with low boost for my silvertop.
One of the twincammers (http://www.twincam.info/index.php?sh...12579&hl=turbo) did a TD04 with LT8S, stock silvertop engine, Apexi B&P Cooler and with 5PSI managed 160 HP ATFW (119kW can't find dynochart at teh moment), considering these things make 74-84 kwatw stock. (http://www.twincam.info/index.php?showtopic=10946, http://www.twincam.info/index.php?showtopic=19191&hl=)
I have been chatting with JFallen about this too. I downloaded his spreadsheet, changed BSFC to .51, put in 138 Fly kW, Max Eng Speed of 8000 (current rev cut is 8200), 8PSI boost (= 1.543 Pressure ratio), with 77x81 engine 4 Cyl and it gives a flow rate of 20.7 lb/min at 8000 rpm. It sized my injectors at 308CC min req and gives you some data to start looking at matching your turbo to these requirements.
He reckons iwth a T3 with 60 that it should get positive pressure from 2500 and be at full boost by 3750. And I would have the added temptation of pushing up to 12PSI as I upgraded things.

[30psi 4agte]

I am interested in why you think/know you have "harmonic issues" with your plenum? How does it manifest? And is that avatar a pic of your engine?

Cheers

David

I have a massive amount of harmonic vibration through the inlet manifold. I have braced it to try and stop it from vibrating. It has worked to some degree but i still keep cracking the manifold from the vibration.
The motor is balanced so its not that that is causing the prob. It is def a harmonic issue.


yes the avatar is my motor> can see pics of the plenum here

http://www.toymods.net/forums/showth...=300rwkw+4agte

I have got that fed up with pulling the manifold off to weld it every time it cracks that i have cut it in half !! along the runners and joined them with silicon hose to stop it from cracking!!!

[dank]

Bit of a grave dig here, but did anything every eventuate with this idea?

I've just read the whole thread and I'd love to know what happened if Sam ever went through with his plan

[Sam_Q]

grave dig? there wouldnt even be bones left now

no I didnt go through with it because I stayed atmo, however I did find some aftermarket high quality pistons for a 20v engine that have a compression ratio of around 10:1. I can share this if you like.

[jonathan yee]

damn i just read the whole thread then found out at the end how old it was, in the meantime my brain was trying to comprehend everything and see if it could come up with some useful advise. OW!

only thought of one thing. to get the turbo spooling late/laggy i'd have a good set of extractors coming of the head and have the turbo mounted with a largish housing after the runners all collect.

that way you'd ahve a nice set of extractors for the whole NA and scavenging effect and the turbo wouldnt come on boos very early as alot of the heat energy would've dissapated.

[jonathan yee]

also they turbo hicomp bike eng's. these dudes do the bmw engines with 10:1 and higher comp ratios.http://www.rbracing-rsr.com/bmwturbos.htm

[-GT-]

The BMW 3-Litre twin turbo is quoted around teh interweb as 10.2-10.5:1 comp ratio from the factory.

[Sam_Q]

d

only thought of one thing. to get the turbo spooling late/laggy i'd have a good set of extractors coming of the head and have the turbo mounted with a largish housing after the runners all collect.

that way you'd ahve a nice set of extractors for the whole NA and scavenging effect and the turbo wouldnt come on boos very early as alot of the heat energy would've dissapated.

interesting idea but it wouldnt work, all harmonic resonant effects would be made null but the turbo. Even if this was not the case you would need primary pipes that would be stupidly long to get a primary resonance below the spool point. In theory however you could have long intake trumpets that might work for you before you hit boost.