zvhturbo

Had a telephone conversation with a well known tuning compnay who told me my 2.1ltr ZVH would reach peak power at about 5000rpm and thereafter would loose power and struggle to rev causing a very poor top speed.

Does this sound true to you guys??

Is there any way of getting the engine to pull all the way to say 6500rpm without the power tailing off at about 5000rpm?

Thanks

Matt.

SPADGE

I would guess that would depend on the engine spec,type of turbo and your bollock/wallet size!

Jim Galbally

he meant that your ZVH wont rev, not that all turbo engines wont rev...

lego engines are known for not being particuarly revvy

Christian and Beccy

iTrader: (14)

Yes, but you will sacrifice low down power.

Turbo's have a relatively narrow power band. You can have BIG power until 9000 RPM if you want, but you will need a big blower that wont come on boost until 5000rpm and what good is that?

Rolls

iTrader: (2)

but if you give it a good spec head, big turbo, then it should produce power higher up the rev range than you would normally expect.........

Christian and Beccy

iTrader: (14)

......and of course a steel bottom end.

zvhturbo

Engine is currently being re-built so the engine spec is what i'm trying to establish.

I mainly want to know what do i need to look at to get the engine to pull 6500rpm with out a drop in power at around 5000rpm??


Turbo is a T34 with 0.48 Ex

Karl

The ability of a turbocharged engine to rev to high rpm's is based primarily on two factors.

1. strength of engine which also encompasses design to be correct for such an application

2. Ability of the engine and turbo to flow sufficent air at these rpm's in order to maintain torque. (this is what makes an engine feel revvy)


The reason the turbocharged ZVH normally suffers with holding high rpm torque is its rated capacity in comparison to the cylinder head flow rate. Essentially this means that the head itself becomes a flow restriction in relation to its capacity and hence engine torque falls quite rapidly with rpm. This can be overcome to some extent with a larger turbo and heavily reworked head which can help increase engine breathing at higher rpm's but this does of course lead to the usual lag, drivability and most importantly cost issues that come about in building an engine capable of using such a large turbo!

hope that helps explain things a little!

zvhturbo

Nope he said Turbo engines in general don't like to rev high

Christian and Beccy

iTrader: (14)

With the right combination of bits, there is no reason why it shouldn't produce power at 6500rpm, however, as others have said, the ZVH isn't notoriously revvy.

A T34 is a fairly good start though. Maybe a 0.63 housing?? But would be a lag monster.

zvhturbo

Thanks Karl, that does kinda confirm things.

1, i use Accralite pistons, steel rods, ARP bolts throughout, main cap studs etc.

2, I use a T34 with 0.48 Ex.

I'm also looking to get a CVH EFI head with 45mm inlets and standard outlets.

Would converting to the Zetec twin cam be better still?

Thanks

Matt.

Phil

iTrader: (1)

Then I wouldn't use that tuning company

Jon ERST S2

I found the 0.55 to be the best in terms of power/lag on the 2.1ZVH.

Here is my graph. Running 20psi.



Peak power is only at 5864. It does still make good power after that but does drop a little. I think it would have been a little higher if I had of had one of Karl's heads. I gather from speaking to a few people that my head was infact ported and with wasted stem penny valves (not larger though) so a proper stage3 / race spec head from karl would probably put it up a little higher.

Karl

Phil,

I would say generically that the above statement is correct. Adding a turbocharger to an engine does usually result in elevated midrange torque and a sharp drop in top end torque making turbo engines feel unrevvy.

A classic example is the R5 turbo or fiesta turbo. Both these cars feel breathless after 5500rpm, whereas their N/A equivalents (e.g. 205 1.6gti etc) are far more revvy.

However turbo engines can be made to rev, (allthough never as well as an N/A) but it's always at the sacrifice of low rpm turbo response.

SPADGE

Lol please subtract 10% before showing us that graph again You'll be getting your Trax 0-60's out next

Jon ERST S2

lol mine wasn't done in 3rd gear!!!

SPADGE

Jon ERST S2

it was done in first

foreigneRS

but doesn't it sound strange that turbo engines don't rev, when the whole thing about a turbo is that the more you spin it, the more air it will pump?

you'd think that like jet engines, the difficult thing would be holding them back

Karl

No foreignrs you're simplifying the process too much.

In an unlimited air flow situation yes a turbcharged engine would run itself into destruction until it could literally spin no more and failed.

In reality there are far more components in the engine itself that limit air flow such as the cylinder head, camshaft and manifolds/exhaust just to name a few.

Remember the feeling of a revvy engine is produced by an engine that has the ability to HOLD torque. In order to do this the flow rate of all the above named components must not reach 100% early in the rpm range, else the torque will fall from this point onwards.

foreigneRS

thanks for the explanation karl

like you, i am also a trained (although not chartered) mechanical engineer in the automotive industry and (more or less) fully understood these things before you made your point.

not meaning to crtiticise you for replying in an intelligent and constructive manner (which is appreciated by me more than most on a lot of topics), in this case i made my post in a deliberately simple way in the hope that it would bring further understanding for others.

you answered in exactly the way that i had hoped, and saved me basically typing out the answer to my own question. and it's a fact that your word's of wisdom are taken a lot more seriously on here than mine.

so my cunning tactic worked

Karl

LOL

I thought as much mate as I knew you knew the answer!!

Stavros

Not really, compared to va bigger engine of course, but thats stupid.

A LOT wider powerband than a N/A engine of the same capacity and the same power.

Simple reason people say turbo engines dont rev is cause they set up wrong, mainly tiny litte turbos that turn out of puff at high revs.

Properly specced theyl rev just as well as N/A

mattbibs

quality post!

zvhturbo

So would it be possible to overcome the air flow problem at high revs by using the Zetec Twin cam head??

Andy-R

The Greenshed(ZVH) did pull high RPM.
Does anyone have a graph showing where it made its peak power?

From what I recall it peaked around 7k!

ballin

iTrader: (1)

pmsl, right

creedy

mine ZVH peek power is at 5216rpm 212bhp 236 torque at 14psi.

zvhturbo

How does it feel after 5216rpm?? Does it begin to feel gutless?

M Brian

jeez it aint wrong is it!! ZVHs don't rev!!


i've got one and its not really impressing me. the car feels mental as i have to so frequently upchange and it makes it a very busy drive - but it only has a real useable power band of 2500rpm (i.e. on bost 2500-5000) ok mine isnt set-up and prob has loads more problems adding to it.
but for everyone elses peaking before 6k... youd be forever changing up into 5th to accelerate or stop the wheel spinning?

how much can you do to push the revs up with cam timing etc?

creedy

yeah it does but thats when i change gear. it feels as if it wont go any higher just stops at 5216rpm.

M Brian

same as mine.

what spec is it? cam wise turbo, managment etc etc

is it like that in all gears?

what happens in 5th?

paulp

didnt soys zetec turbo only rev t0 5000rpm, i remember reading that in the feature, also i thought the whole point of fitting a zetec bottom end was that it can rev higher?or i probably am totally wrong

zvhturbo

The zetec can rev higher, i believe its due to the longer rods, crank stroke etc, don't quote me on that though.

The reason Zetec or ZVH engines don't rev so well is due to the head, cams, turbo etc not being able to flow enough air for a blown engine.

It would appear if you could flow the required air then you would pull power to a higer rev threshold.

Stavros

Turbo engines need smaller ports than n/a engines so i dont belive its head flow thats an issue at all if n/a ZVH/Zetecs rev well and turbo ones dont.

Look at Cossies, when going n/a they MASSIVLEY port the head to get any power out of it, but in turbo form it produces the power decently high up without that.

Take off the T3s and put somthing with a fairly big ex housing (well a decently big turbo in general) and youl rev higher.

A T3 and small ex housing isnt going to produce the power high on any 2litre engine, ZVH or not.

Karl

LOL you're all fast learning after many years of me trying to educate you all, why I recommend the 1600 bottom end when using a cvh head.

They don't pull peak power until 7000rpm and then still hold at least 95% peak power at 7500rpm. Total power band is 3500 to 7500, and combined with a relatively flat torque line, allows you to use the power without excessive wheelspin!!

I do build big capacity engines as they drive well at lower rpm's, but I personally dont think you can beat the all round characteristic of the 1600 when keeping with the cvh!

Karl

Steve, you're wrong regards the cossie heads and port sizes. For big power on a turbo engine you need BIG ports as well!

creedy

2.1ZVH, ford motorsport cam, superchip.
yeah its like it in all gears, havent gone 2 5000 in 5th yet so i dnt knw

neal

James_RST

according to the graphs my 1.8 zvh makes the numbers at around 5.5k and tails off after that.

doesnt bother me, i dont keep cars long enough tow orry about new heads etc

Jon ERST S2

So just to clarify it's more the capacity increase that zetec/cvh bottom end?

a 2.1CVH (Which doesn't exist I know) would have the same problems as a 2.1ZVH? i.e more work needed to make it rev higher?