1.8 JH-engine tips?

[kapsu]

Hi and greetings from Finland!

I have a Scirocco GT2 -90 (and Primera GT -99). I'm quite newbie with Scirocco, just bought it few months ago..

Car has 1.8JH engine with catalysator and it is running ok, although lacks some power.. any hints for that?

Because the laws in Finland, we cannot install turbo nor can we remove the catalysator :/ So what can we do... if anything?

I'll try to add some pics..



Post Edited (07-16-05 21:28)

[kapsu]

pics,

[OSLer]

Hello to Finland from Germany!

Nice cars, the Scirocco especially
For tuning the JH is simply the wrong engine, it would cost too much in effort and money to get this engine running smoothly.
Simple things are of course camshaft ( Schrick for example), the damper from Audi 5 cylinder engine + warmup regulator, flatten the cylinder head or polishing the intake and exhaust area.
But all this won´t let you get far over the 105 hp, i think.


Greetings Lars

[kapsu]

Hi Lars, thanks for the info..

What do you mean by that damper from Audi?


Any experiences of replacing the original catalysator with a highflow cat? (eg. MagnaFlow or HJS.)

Or rising the compression ratio from 8.5 to 9-10 by changing the pistons from other 1.8 engine, EV/DX etc.?

[OSLer]

Damper is another word for the air regulator with the flap, maybe throttle(?) the german word for this is Drosselklappe, i don´t know any other or better translation, sorry.

"Or rising the compression ratio from 8.5 to 9-10 by changing the pistons from other 1.8 engine, EV/DX etc."

I think that this is the only way to get more out of this engine, if this is possible for you. Together with the camshaft from Schrick and all other mentioned mods you can get up to 115 hp, if everything is set up correct.
If possible better change the engine to DX, it would be the better base for tuning.
To keep the catalysator regulations clean, just use the puls generator, fuel distributor and the exhaust header of the JH engine.


Greetings Lars

[Tempest]

Is that you in the first picture, kapsu?

Nice Rocco, and welcome to this forum from the UK-outpost

Yes, Lars means the Audi 5E throttle body (German: Drosselklappe), but you must use that in conjunction with the matching Audi warm-up regulator.

As Lars has already mentioned, the JH in standard format is not hat ideal for modifications, unless you're willing to invest lots of money and time. Indeed your ideas of increasing the compression are a solution, but by the time you've done it, you would have been better off having strated with a different engine altogether, like the afore-mentioned DX engine (already has a compression of 10:1, not 8.5:1 like the JH).

HTH,

Tempest

[sublime]

Welcome kapsu,

Most things I whould suggest have already been said, a few members of this board invested time and money into modifying an JH engine with very little effort. The reson is quite obvious when considering the meaning of compression ratio. Compression is directly related to average combustion pressure . The higher the compression, the higher the combustion pressure. This "a.c. pressure" is the most significant attribute for efficiency of an engine. By raising the efficiency, you get more horsepower per fixed amount of fuel/air mixture. It's one way of classic tuning. The other way is to raise the amount of air/fuel mixture sucked into cylinder and another way is to raise the rounds per minute at which the peak torque is available.

You see, by driving a very low compression, lower than the engine layout whould allow at most, you suffer a bad efficiency. This also relates to every tuning attempt you start. As on the one hand a sharp camshaft of about 272° whould boost the max. power of an DX another lets say 10HP up, on the other hand a JH whouldn't be able to use that amount of more air/fuel mixture just as efficient as the DX does, resulting in a lower HP gain (lets say 6-7HP).

Thinking about higher compression should be the first step if serious HP gains are wanted.

Greetz
Chris

[kapsu]

I'm not looking for a rocket, merely checking that what can be done. (Our Primera (150ps) beats it 10-0 :( )

I bought the Scirocco mainly for the looks, great classic =) Scirocco is really a rare car here in Finland.. there wasn't many to choose from. All the originally imported DX and KR/PL models were in pretty awful condition. In the recent years people have imported more Sciroccos and they are usually JH (it seems to be the most common in Germany...)

back to topic:
In our local forums I read that the cylinder head is the same on JH and other 1.8l 8v engines, so the lower compression is due different pistons.. which have bigger combustion area. But besides the pistons, what are the other differences to e.g. DX engine?

Could I just change the pistons from a DX/EV/PB or basicly any other 1.8l 8v mk2 Golf engine (plenty on the scrapyard..)? That would be bolt-on change? What else is needed?
I imagine that would be much cheaper than making modifications to the head or manifolds at some high-price workshop..

[kapsu]

And are there any exhaust manifolds available for JH (that would fit the original catalysator)? I have seen plenty of manifolds for 1.8 8v but..

EDT: I noticed that SuperSprint has manifolds for mkII Golf with cat.. would that fit?



Post Edited (07-17-05 10:55)

[GTX]

Hi!
replacing the original catalysator with an cat-fake wont get you any 0,1HP.
The Problem ist the fu***ng small outtake-manifold.
I have a EV (same as DX) installed instead of the JH-Enginge. All parts from the FI are still JH.

http://forum.rowi.net/read.php?f=10&i=11522&t=11522

My Engine is the pic under : "Ich weiß zwar nicht was der Sebastian für nen Motor drinhat, aber der drückt auf jeden Fall 108,5 PS nach DIN"


Greetings, Sebastian