turbos and high compression??

[MRJDM]

can some some tell me why turbos dont like high compression. cos isnt a turbo charged car essentially a bloody high compression motor??

[tinkerbell]

yes, it is a bloody high compression motor, and therein is the answer! you are doubling the compression, which would be bad.

you have either one or the other, high compression with no turbo or low compression with turbo

this is the most simplistic way to look at it ;)

(the compression ratio will determin how the car drives off boost...)

[tinkerbell]

oh and the reason why is because high compression plus turbo is very hard to get good reliable power due to the amount of timing you have to take out to get it NOT to detonate or ping...

[pornstar]

oh and the reason why is because high compression plus turbo is very hard to get good reliable power due to the amount of timing you have to take out to get it NOT to detonate or ping...

:confused:

[tinkerbell]

the higher the combined compression ratio:

the less timing you can run...

or,

the higher octane fuel you need...

otherwise there will be pinging, knock or detonation.

[tinkerbell]

this is why ITR's with turbos rarely run more than 7-10psi on stock internals...

[vtml]

Tuning window is smaller on a hi comp engine as compared to low comp engine.

[SiR JDM]

very informative tinkerbell, ive learnt a bit

wat would u think about b16a then.. if i were to ever consider turboing it..
its got a compression of 10.4 ...?

[2ds]

no problems, you just can't run too many psi on stock internals (as tink said before)

-2ds

[poid]

Sir JDM you just have to be a little more careful with the tuning

[tinkerbell]

very informative tinkerbell, ive learnt a bit

wat would u think about b16a then.. if i were to ever consider turboing it..
its got a compression of 10.4 ...?

yes - very good engine to turbo charge.

as long as boost is kept below about 8psi and you can tune it with aftermarket ECU (or piggyback if desperate)

you can get thicker headgaskets (eg 2mm) that reduce the compression to around 8 or 9:1 - or you could install lower compression pistons along with forged rods for extra strength - then boost it a LOT! (se BLKCRX's 400kw for example)

i have been informed that 130 - 150kw ATW is attainable on a stock B16A with turbo and proper engine management, probably able push it higher (but with greater risk of damage)

i have never done this so am only refering to discussions that i have had (when i was considering turboing my B16A)

i learnt lots from honda-tech.com boosted forums too
:thumbsup:

[pornstar]

135kws from the b16a is attainable at about 6-7 psi

[WPN.22R]

i pumped 15psi through my motor standard, but had a 2mm gasket on to lower the comp!!

[Type R Positive]

you could fart into a b16a and get over 200kw atw on stock internals.
Great engine.

[Weq]

i pumped 15psi through my motor standard, but had a 2mm gasket on to lower the comp!!

so what did that achieve?? more boost, less power per psi. less chance of knock, maybe putting the turbo into itsd efficency range?

[shecomb]

Would just help for reliability and longevity...

2mm gasket lowers the comp so theoretically you can run more boost on a stock engine

Not really any power difference

[Weq]

less comp = less power = less effective compression. u wouldnt pump 15psi through a standard h22 without some balls.

[rev-tech]

why don't turbo's work with hi compression.

it's called a flash point. Where the compression in the engine heats up the air/fuel mixture so much that it ignites by itself without the aid of a spark.

i think the flash point for normal fuel is around 15:1.
and i THINK every 3psi you raise up it up's the CR by 1.

essentially in a boosted engine as you wind up the boost your just increasing compression. When the CR of the engine combined with the boost level get's over the flash point you'll get detonation and i think most people know what happens then.
Thats why you can lower compression to increase boost etc etc.
the main other factor in detonation is heat.....if the air is already hot before it enter's the cylinder then it heats up even more.

[tinkerbell]

and i THINK every 3psi you raise up it up's the CR by 1.



that is close, but this is a table of compression vs boost:
http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=308
(sorry - you need to register)



the main other factor in detonation is heat.....if the air is already hot before it enter's the cylinder then it heats up even more.

why efficent intercooling (water to air or air to air) allows you to run more boost safely :)

[tinkerbell]

ie the table shows that at a static CR of 8:1 a boosted engine will be creating a compression ratio of:

2psi = 9.1cr
4psi = 10.2cr
6psi = 11.3cr
8psi = 12.4cr
10psi = 13.4cr
12psi = 14.5cr
14psi = 15.6cr
16psi = 16.7cr

"The numbers in the chart in bold indicate the safe zone of operation for a non-intercooled, Supercharged or Turboed vehicle running moderate timing with 92 pump octane (USA) gas and Stock Internals."

[rev-tech]

i think i know the table you've talkin about.....i've seen it before in a book on turbo's
VERY useful!

basically running a turbo in (or under) it's efficency boost range. Too much above this range and it will develop a hell of alot of heat! which is just wasted energy

[pornstar]

ie the table shows that at a static CR of 8:1 a boosted engine will be creating a compression ratio of:

2psi = 9.1cr
4psi = 10.2cr
6psi = 11.3cr
8psi = 12.4cr
10psi = 13.4cr
12psi = 14.5cr
14psi = 15.6cr
16psi = 16.7cr

"The numbers in the chart in bold indicate the safe zone of operation for a non-intercooled, Supercharged or Turboed vehicle running moderate timing with 92 pump octane (USA) gas and Stock Internals."

i assume on one turbo size on one particular ambient temp for one particular piping length, for one particular type of intake piping metal?

[tinkerbell]

i assume on one turbo size on one particular ambient temp for one particular piping length, for one particular type of intake piping metal?



http://www.team-integra.net/section...p?ArticleID=308
(sorry - you need to register)

it says these are non-intercooled numbers ;)

[pornstar]

yer hence why im asking about ambient temps, turbo size, and intake material :)

[tinkerbell]

your assumption that these are the same for all calculated CRs is probably correct.

[PhatSol]

Just noticed that the stock B16A2 compression is off that chart... Not much safe boosting area :p

[tinkerbell]

Just noticed that the stock B16A2 compression is off that chart... Not much safe boosting area :p

remember the chart is indicative of estimated CR's of non-intercooled setups... ;)

[PhatSol]

remember the chart is indicative of estimated CR's of non-intercooled setups... ;)

Well I guess that makes intercooling on the VTEC motors *very* important then?

[tinkerbell]

yes, exactly, any turbo/supercharged engine will benifit from intercooling as it reduces the intake air temps -> denser intake charge -> more power & less chance of pre-ignition

[2ds]

Well I guess that makes intercooling on the VTEC motors *very* important then?

even more important is not using 92ron US pump gas =p

-2ds

[[Blitz]]

even more important is not using 92ron US pump gas =p

-2ds

That's right, the higher octane, less chance of detonation and more advance in the timing you can run, leading to more power.

[poid]

US 92 octane is only a touch worse than our 98 RON fuels ;)

[tinkerbell]

it is better than our 'regular' unleaded...

[rev-tech]

those calculated CR's would most likely be correct (as long as theyw ere done right)

The detonation point would change depending on the effency of the turbo/intercooler

[WPN.22R]

148kw atw without working internals just gasket only ... i think that acheived a bit... one thing id mention is all the tossers who said that it couldnt or shouldnt be done!

but that was my basic bolt on set up way back then. now ive put the standard size gasket back on and got forgies...and other stuff, i was hitting 130 something kw atw on 10psi, without revving past 5k!!

[ProECU]

There are two schools of thought for boosting engines & CRatios.

U can run high CR with a long overlap cam to bleed dynamic CR.

The real reason why boost + high CR is "perceived" to be a bad idea is becuase ignition of a compressed mixture is not only harder to achieve in the same amount of time, it also becomes unstable.

Personally, after researching this topic, It's my opinion that a moderate / High-ish CR + boost and correct cam timing is more advantageous over low CR + boost.

I wonder why the B16 responds well to boost in stock form....... But what would I know right?

[PhatSol]

The real reason why boost + high CR is "perceived" to be a bad idea is becuase ignition of a compressed mixture is not only harder to achieve in the same amount of time, it also becomes unstable.

So would you say that a more powerfull ignition system (bigger gap, fatter spark) could help here?

[ProECU]

yes, but remember, efficient combustion is a controlled burn.

[EKVTIR-T]

hey just curious,where you guys pull your power estimates from?

[tinkerbell]

hey just curious,where you guys pull your power estimates from?

things i have read & seen and people i have talked with.

[Honda_Fools]

*bennjamin edit*

Sounds like another troll on the forums...

[Lyle_Style]

once you boost a motor it is upping the compression on it anyway,
hence a motor with a standard high compression like 10:1 or 11:1 will only handell a small amount of boost on average eg 5lbs. ideal compression for a turbocharger is around 7:1 or 8:1 this can be achieved by useing a decompression gasket or some dished forged pistons.
A non vtec motor will be easier to turbo charge because they have a lower compression then the vtec. Most D series non vtec motors are around 9:2:1 which can handell around9lbs on standard internals. A b16a or h22 would only handell around 5psi standard

[PhatSol]

once you boost a motor it is upping the compression on it anyway,
hence a motor with a standard high compression like 10:1 or 11:1 will only handell a small amount of boost on average eg 5lbs. ideal compression for a turbocharger is around 7:1 or 8:1 this can be achieved by useing a decompression gasket or some dished forged pistons.
A non vtec motor will be easier to turbo charge because they have a lower compression then the vtec. Most D series non vtec motors are around 9:2:1 which can handell around9lbs on standard internals. A b16a or h22 would only handell around 5psi standard

Dropping down to 7:1 and 8:1 is a little excessive for a street car don't you think, especially a B series?

[Weq]

whats the average lifespan of a thick, decompression headgasket? There is alot more material then a normal gasket, so wouldnt i get eaten away easier/faster? opinions?

[PhatSol]

whats the average lifespan of a thick, decompression headgasket? There is alot more material then a normal gasket, so wouldnt i get eaten away easier/faster? opinions?

That is a factor, but from what I have read/heard the biggest issue is that you are reducing the quench because of the increased clearance between the piston at TDC and the head. Which of course increases the chances of detonation... Having said that though, some of the results Mr Toda has posted for stock B16A with thick head gasket are pretty impressive :)

[Lyle_Style]

Dropping down to 7:1 and 8:1 is a little excessive for a street car don't you think, especially a B series?

Maybe a little excessive, but i know a bloke running a 6:2:1 compression with tough thick gaskets and all forged internals and its basically preped for 35psi
but yeh basically just how much boost u want, the more u want the lower you go and the deeper your pockets have to be
8:1 is a good compression as it will be still pretty torquey off boost down low and be able to easily handel 15lbs - 18lbs safely (depending on your cooling setup of course)