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View Full Version : Exaust and backpressure



GoLfMan
24-05-2005, 12:22 PM
With my 1976 3 door golf which i am doing up to race, i was thinking of a 2 1/4inch stainless steel engine to outlet system. does anyone know what the 'right' kind of exaust and back pressure is needed for best performance :?:

Golf Loon
24-05-2005, 11:18 PM
That sounds quite large. What size engine is it? If you dont have enough backpressure, you`ll lose heaps of go. I`m thinking 2.5inch for my 2L 16v
That size with a 1.6 would be no good though.

Anonymous
25-05-2005, 03:30 PM
yeh sorry i forgot to say... its a 1600 carby.... yeh i think ill just leave the stock piping in there and put on a new muffler... do you think that will work at all?

GoLfMan
25-05-2005, 03:32 PM
yeh sorry i forgot to say... its a 1600 carby.... yeh i think ill just leave the stock piping in there and put on a new muffler... do you think that will work at all? that again is my post i keep forgettting to log in :x

Golf Loon
25-05-2005, 07:33 PM
Has it got extractors? They make the 1600s howl, especially if you drill out the main jet in the carby, or replace it with an auto one.

GoLfMan
26-05-2005, 10:30 PM
no i havent got extractors atm... stock as a block . but i have a carby that i got off my renault 15 (which is going to wreckers tommorow :( cos it has so much rust) and the carby is a double barrel (both barrels 41mm ) webber. :D but the manifold bolt pattern doesnt match up. will i be able to fit this carbi on?
i was wanting extractors :D

Golf Loon
27-05-2005, 12:08 AM
If you can cut and weld up a golf inlet manifold, you might be able to make it fit. i think its alloy though, hard to weld.
I`ve got some brand new extractors, which dont fit my 16v. 200bucks never been on a car.

GoLfMan
27-05-2005, 08:15 AM
well ill take my car to Volkspower to see what they can do, and to see if the carbi is worth putting on. im a Melbourne man. extractors you say? 8) would they fit a mk1?

Golf Loon
27-05-2005, 09:34 AM
The extractors are made for a Mk1. I paid 300 for them, but have now got a 16v, so dont fit my car. Bargain $200 postage $40approx

GoLfMan
27-05-2005, 12:03 PM
Ill think about it :) .... thanks :)

GoLfMan
30-05-2005, 12:46 PM
im seriously thinking about those extractors :) but CV Joints and wheel bearings are first. with the exaust i was thinking just leave the stock piping and put a free flowing muffler on it. would that do any good?

Golf Loon
30-05-2005, 10:50 PM
The golf exhaust is so basic that it couldnt really restrict flow even stock. The worst bit is the manifold and downpipe which strangle it. Thats why everyone goes extractors in the end. FLOW = GO

GoLfMan
31-05-2005, 10:05 AM
hmm sounds good. have you still got those extractors that you wanna sell? cos i want them as soon as i get the money. also that webber your seeling for the golf. the delorto can i trade you a downdraft weber double barrel 41mm for that??

TassieGTi
02-06-2005, 09:38 AM
The Renault carby will make a great improvement.I have a 2 barrell manifold and an 2 into one adaptor if needed.
Better still I have a side draft dellorto and manifold.
If you use a 1600 motor don't go bigger than a 2 inch system, the original twin manifold downpipes are quite efficient and there are very small gaines by using extractors but 2 ich system and free flow muffler certainly gives a noticable improvement.

GoLfMan
02-06-2005, 02:51 PM
i should take some fotos , so this adaptor can you chuck some fotos my way???.. you have twin delortoes and manifold how much do you want for them? :D

Belgianwaffler
06-06-2005, 10:26 AM
it's not so much back pressure that is the issue but gas speed .... what size is the engine ? what RPM will it be running at, etc....

Belgianwaffler
06-06-2005, 11:50 AM
Sorry had'nt notice there was a mention of 1600 carby :? for a 1600 to about 6500 RPM and a mild cam, rejetted carby I would'nt go over 1 3/4 inch .... if you get a single webber /dellorto & links maniflod and a MK3 exaust manifold with the downpipe (mods reqired) you should be able to get a nice strong power band.... take the intake valve to 38mm with a 3 angle job (mild street port) and it'll be even better.

GoLfMan
06-06-2005, 12:34 PM
thanks mate. i shall take all these things intom consideration!!!!

gldgti
04-07-2005, 07:21 PM
I know a guy that almost did up some golfs for rallying. i say almost because he got suckered into using suzuki's instaed - go figure... anyways

he had a 1600 bored to 1800 with delorto carbie on it, some fancy camwork and a stainless 2.25" system to go with it, and reckoned it was good for 200hp.

anyway, what i was getting to was...you dont need a massive system for power - like everyone is sayin... im jealous too - the day i have a spare golf i can race i'll be :lol:

GoLfMan
04-07-2005, 07:47 PM
I know a guy that almost did up some golfs for rallying. i say almost because he got suckered into using suzuki's instaed - go figure... anyways

he had a 1600 bored to 1800 with delorto carbie on it, some fancy camwork and a stainless 2.25" system to go with it, and reckoned it was good for 200hp.

anyway, what i was getting to was...you dont need a massive system for power - like everyone is sayin... im jealous too - the day i have a spare golf i can race i'll be :lol:

well i got 2 golfs goin atm... racing one :wink: ooo yehhh.. yeh im getting the delortoe coming... i sent off money... now its the waiting game lol can wait to get my hands on em... then a nice hot cam and the exaust sounds great... a simple yet effective race car :twisted:

finemk1
07-07-2005, 10:30 PM
on that exsaust issue, i had a full 2 1/4" fitted to me 16v mk1 with to hotdogs and a back box, unaware the back muffler was a cheapo the motor killed it, mounts were snapping and i slaughted 2 flex joints in 3 months ,rear muffler was getting crazy hot and eventually burnt the inside flanges off and a big lack of power was lost i had that muffler for bout 5 weeks befor it was dead, now its a 'superflow' straight through box with 3 " tip, ,instant power back really good choice.......
i never relilsed an exsaust could make that much difference to performance so shop around and ask lotsa question befor u get one made up and inpsect your hardware befor dodgy ass muffler men stuf your car up..

20v kit car
08-07-2005, 09:42 AM
200hp with a single delorto 1.8 where did he hide the hair drier ????

TassieGTi
08-07-2005, 10:11 AM
He may have meant 100 hp I recon ,people love numbers.

GoLfMan
08-07-2005, 10:15 AM
He may have meant 100 hp I recon ,people love numbers.

isnt the rule of thumb 1/10 of your capacity is the peak power you can achieve naturally aspirated?? for eg 1600 is 160hp and so on

TassieGTi
08-07-2005, 10:21 AM
That rule of thunb may apply to factory developed big budget motor but a norm from the suburbs would be lucky to get 100 with that combo.Lets be realistic.

GoLfMan
08-07-2005, 10:24 AM
fair enuff i agree with that. if he put a blower on there he coulda got that sorta power though

Golf Loon
09-07-2005, 12:15 AM
I reckon 100 is realistic with that motor.
A supercharger or turbo would be fun though :shock: :twisted:

Belgianwaffler
11-07-2005, 12:20 PM
single dellorto will flow about 90 hp
from memory ....

now twin with bigger chokes that should be nice ...

GoLfMan
11-07-2005, 12:23 PM
wat will the twin do from memory??? is that 90hp just from fitting the new carbi?

Belgianwaffler
13-07-2005, 12:57 PM
with the twin delorttos you should see about 140 - 150 HP (flywheel) from a ported MK3 8v head (they had 7mm stems).
In Denmark my Uncle had a 16v with a 1600cc bottom end wich was pulling 213 HP flywheel at 8700RPM (twin delorttos) that was back in the late 80s

GoLfMan
13-07-2005, 02:55 PM
jesus.. :shock: i just got the 1600 8v engine... so ill get bout 100hp??? round bout? at the flywheel

Golf Loon
13-07-2005, 07:58 PM
If the engine has extractors, a cam and a better carby. 100 if not, maybe 80?

GoLfMan
13-07-2005, 08:05 PM
extracors cam and exaust are next on the list :D

Golf Loon
13-07-2005, 08:13 PM
The HP readings in the Golfs case, do not reflect the speed and handling. Its the whole package and I LOVE IT.

GoLfMan
13-07-2005, 10:07 PM
The HP readings in the Golfs case, do not reflect the speed and handling. Its the whole package and I LOVE IT.

my dellortoes should make it go like stink... i agree. cos its such a light car with direct steering.. a great package.. i love it also soo entertaining to drive :D cant wait to get some sport suspension improve handling further :P

VanKronenburg
14-07-2005, 05:25 PM
he had a 1600 bored to 1800 with delorto carbie on it, some fancy camwork and a stainless 2.25" system to go with it, and reckoned it was good for 200hp.

If it was that easy, many tuners would be out of a job. I could write you out a list several pages long for getting 200hp from a 1.8 8v engine.

It is difficult enough to get an HONEST 200hp from a very modified 2.0 16v. :roll:

VanKronenburg
14-07-2005, 05:29 PM
with the twin delorttos you should see about 140 - 150 HP (flywheel) from a ported MK3 8v head

Not a chance my friend. To get the Golf 3 8v head to flow any CFM requires 41mm inlet valves and some very serious work :wink:

GoLfMan
14-07-2005, 09:48 PM
VanKronenburg how much power would i get when i strap on my doubble barrel dellortoes onto my 1.6 8v??

VanKronenburg
15-07-2005, 08:00 AM
Perhaps 5-8ps... Remember that when you give an engine the opportunity to breathe more air it must be capable to do so, otherwise the power gains are very small. So if you install twin carb or throttle bodies to any motor, you need to upgrade the camshaft to allow the air to enter. Then, you must also upgrade the head to get the best from both the carbs and the cams and generally to restore midrange torque. Placing induction mods on a standard motor will flatten the torque curve more than it will add power. It will sound nice, though :P

GoLfMan
15-07-2005, 09:40 AM
camshaft was next on my list of things to buy.

Belgianwaffler
18-07-2005, 03:29 PM
Hi VanKronenburg... well I referring to flywheel figure yes it would be hard but not impossible ...40 mm valves -> +/- 30hp in street trim per cylinder.With minor porting you should be able to get around 34hp

41 mm valves -> 33hp street trim

41 mm valves would'nt be hard to fit .... okay in the end it's the cost.

Belgianwaffler
18-07-2005, 04:07 PM
Hi again for those who are interested and have the cash to play ....
I have just been searching for ways to improve power without force induction.
I'm in the process of finishing a 16v head with a valve swap;
33 mm intakes with 6mm stems, std 28mm exaust valves. the head is a 2.0l head which is reported to flow well on the exaust side.
There is no porting on the head except for the seat work which had to be done to accomodate the larger valves. ("radiussing" of the seats as well).

the valves (intake) are from a 2000 ford focus "zetec" engine and are the oversize option. at 97.5 mm long they are 2mm longer than std vw intake valves... the seats in my head were not recessed and I was able to check lifter clearance which was around 1.5mm... of course I had to get some valve guides made up as 6mm would be quite loose in the old ones..

VanKronenburg how good are the std 16v springs ???

VanKronenburg
18-07-2005, 09:08 PM
Hi,

The stock 16v valve springs are safe >7500rpm and to 11.5mm of valve lift. They should be replaced with new VW items with any mild camshaft upgrade or head rebuild. With a cam that needs more than 7,500rpm, one shouldn't use the standard springs.

The largest cam we recommend with the standard springs is the 268/11.5mm by Schrick.

The ONLY aftermarket valve springs worth using are made by CAT CAM, Dbilas, Schrick and our own in-house items. The rest are no better than a stock VW item.

Regarding the work you have just done to the 16v, I don't want to sound as though I am telling you what to do as it's good for people to try different things, but the modifications you describe won't aid the flow in any way.

The blockage in the 1.8/2.0 16v head is in the exhaust side, due to the near 90 degree exit bend. This needs reshaping without enlarging it much more and is where the majority of work needs to take place on this head. There is no point enlarging the valves on any cylinder head without first impoving the casting itself.

There are 6 major problems that should be adressed in a well modified stage 1 16v head. Further than this, stage 2 and 3, port shape can be considered more carefully, as can multiple-angled valve seats. Next, a valve upgrade to 34mm/28.5mm is the best option. Obviously there is much more involved than this, though!!!

I am first to admit that this is not a well designed head. The OPEL 20XE is a far better head and much easier and less expensive to modify well. :D



Hi again for those who are interested and have the cash to play ....
I have just been searching for ways to improve power without force induction.
I'm in the process of finishing a 16v head with a valve swap;
33 mm intakes with 6mm stems, std 28mm exaust valves. the head is a 2.0l head which is reported to flow well on the exaust side.
There is no porting on the head except for the seat work which had to be done to accomodate the larger valves. ("radiussing" of the seats as well).

the valves (intake) are from a 2000 ford focus "zetec" engine and are the oversize option. at 97.5 mm long they are 2mm longer than std vw intake valves... the seats in my head were not recessed and I was able to check lifter clearance which was around 1.5mm... of course I had to get some valve guides made up as 6mm would be quite loose in the old ones..

VanKronenburg how good are the std 16v springs ???

20v kit car
18-07-2005, 09:54 PM
hanse it good to see another member giving good advice based upon experience and not rule of thumb stuff..i agree with all the principals you just outlined.Most of my experience is via a family owned vag shop and Oettinger for which we are the australian agents past 10 years.the research and development gained by oettinger in their early days was great..today these developments are less..more suited to chip tuning.I learnt alot about head porting via oettinger and its a art that must be taken seriously..the lehman cyl head from the kit car is very unique along with the 7 cut to the surface.VWM 265hp 16v is so close to the edge every time its revs your in heaven...i've been informed by VWM that the bosch ecu in the kit car should have a battery change every year..you heard of this or is it a revenue raiser....also believe an upgrade due to intake port size variation and mapping is altered to suit any thoughts,as you may expect trying to get this info in our country is non existant..thanks for any info you can put my way cheers steve muller

VanKronenburg
19-07-2005, 09:38 AM
i've been informed by VWM that the bosch ecu in the kit car should have a battery change every year..you heard of this or is it a revenue raiser....also believe an upgrade due to intake port size variation and mapping is altered to suit any thoughts,as you may expect trying to get this info in our country is non existant..thanks for any info you can put my way cheers steve muller

If they say to do it, then I would be. They earn enough money to mean they needn't revenue raise!! :lol:

It does seem a strange thing to do, however. I can find the answer to this quite easily if you'd like? I don't know off the top of my head so will have to check it in one of the tech manuals.

Either way, given that good VW parts seem so rare in Australia, I wouldn't be taking any risks with anything!!

With your other question, do you mean if you change the inlet port size/shape on the head, should you alter the ECU map?

Belgianwaffler
19-07-2005, 12:57 PM
point taken VanKronenburg ... my personal favorite is the BP-ZE mazda head ... not to sure if we get the "Opel" 20XE around here ..note however that the local market "Holden" 4 cyl s are rebadged Opel cars

GoLfMan
25-07-2005, 12:57 PM
that would prob be the holden astra engine yes>?

el_foolio
25-07-2005, 01:05 PM
yep they are, we have a holden barina, thats rebadged as opel, it has an opel engine, at least its european :P

Golf Loon
22-07-2006, 08:06 PM
Was searching for extractor info, but this is a good post about 16v head porting.

gtimk5
23-07-2006, 07:43 PM
This is very interesting stuff on the 16v heads indeed but the topic started out on extractors for an 8v. Maybe we would all benefit from a new topic on modifying 16v motors and tuning such. I am very interested and you guys obviously know your stuff and have a lot of experience with them.
(Me???) I know how to snap exhaust cams on them!!!!:)

ontarv
24-07-2006, 07:54 PM
just read this thead my 8v was running
straci's and 2 n 1/4 with hot dog n muffler
but has big cam and big valves they nearly
touch. found the exhaust to be good from
the 1 n 3/4 that it replaced.