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Author Subject: Cams on GTI-6
makaveli144

Newbie

Location: Burton

Registered: 23 Feb 2010

Posts: 31

Status: Offline

Post #1
Im looking at buying a GTI-6.My previous car was a throttlebodied saxo VTS.

I realise the performance wont be close to that of my saxo. I was wanting to cam and throttlebody the GTI but since reading through the site I realise the pistons have to be changed to run wildish cams. so my question is what is the wildest cam that can be run on standard pistons and what sort of power will this give.

Cheers for any help
Posted 24th Feb 2010 at 18:51
dented_vts

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Location: london

Registered: 23 Feb 2010

Posts: 440

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Post #2
You would be better off spending money having the head ported properly first, only then change the cams if you need to.
Posted 24th Feb 2010 at 19:00
ken

Senior User

Location: wokingham

Registered: 28 Mar 2007

Posts: 905

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Post #3
mine has race cams in! and runs fine. i have been told to get the head ported aswell! which i will be doing!

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Posted 24th Feb 2010 at 19:30
dented_vts

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Post #4
What profile are the cams you have? If you port the head properly you should see benefit across the rev range however fitting cams will loose you a bit at the bottom end. I personally IMHO don't see the point in fitting longer durations cams to a standard head, you will see much more benefit if you fit the cams to a well ported head. But the problem is where do you go for head work? I expect a good big valve gti-6 head would cost at least a
Posted 24th Feb 2010 at 19:41
makaveli144

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Location: Burton

Registered: 23 Feb 2010

Posts: 31

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Post #5
My saxo was very peaky.no power below 3k revs and peak power at 7.6k so I wouldnt mind losing some low range on the GTI as Im used to it.getting the head sorted is a good idea though. QEP did my old head.

What cams are you running ken?
Posted 24th Feb 2010 at 19:49
ken

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Location: wokingham

Registered: 28 Mar 2007

Posts: 905

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Post #6
not to sure mate. i think maybe pt80 - pt82

:s lol

but my mate cab port the head on my wallye but it wasnt going to be a k

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Posted 24th Feb 2010 at 19:51
pugheaven

Seasoned Pro

Location: Fareham

Registered: 17 Dec 2006

Posts: 4,602

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Post #7
not race cams, fast road probably. You can see 200hp with a set of 270s and head with maniflow manifold. With throttle bodies say 210-220hp. Doesnt cost alot to pocket the pistons tho
Posted 24th Feb 2010 at 22:49
rallyeash

Seasoned Pro

Location: Devizes

Registered: 11 Dec 2006

Posts: 4,424

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Post #8
the term "race" makes me laugh sometimes..

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Posted 24th Feb 2010 at 23:03
petert

Newbie

Location: Sydney

Registered: 18 Mar 2007

Posts: 38

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Post #9
dented_vts wrote:
You would be better off spending money having the head ported properly first, only then change the cams if you need to.


You're dreaming. The head already flows more than most "ported" other make heads. The limitation are the small camshafts.

You can run up to approx. 0.060" lift at TDC before entering the danger zone.
Posted 25th Feb 2010 at 10:31
daveyboy

aka Jim Davey

Location: Southampton

Registered: 01 Oct 2007

Posts: 8,648

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Post #10
All the tuners I have spoken to say leave the head alone, just smooth any rough edges and ease the throats a little to eliminate any shrouding. PT82s should go in but horror stories are out there of valve to piston interference. PT80-81 seem pretty safe but the thing to do is during fitting check the clearances so you know how far you can safely advance them. And FYI race cams are usually 300 degree profile at least Wink

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Posted 25th Feb 2010 at 13:39
welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

Posts: 25,817

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Post #11
amusing "race cams" comments and "get it ported" LOL

re; clearance in the stock engine, there's no way race cams will fit in there without larger cutouts and often machining to the head for lobe clearance.

scary/informative thread linky

you'll get around 167=190 odd on the stock inlet with some cams SAFELY if you want nearer 200 you'll need the pistons modifying or different ones.

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Posted 25th Feb 2010 at 14:16
daveyboy

aka Jim Davey

Location: Southampton

Registered: 01 Oct 2007

Posts: 8,648

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Post #12
welshpug! wrote:
amusing "race cams" comments and "get it ported" LOL

re; clearance in the stock engine, there's no way race cams will fit in there without larger cutouts and often machining to the head for lobe clearance.

scary/informative thread linky

you'll get around 167=190 odd on the stock inlet with some cams SAFELY if you want nearer 200 you'll need the pistons modifying or different ones.


Ouch! Shock

________________________________________

R H Davey Welding Supplies. I sell new and used welding equipment in the Hampshire area. I take on welding jobs in the evenings, ally casting repairs are one of my specialities but I can weld pretty much anything. PM me with your requirements.

Some of my services: (See my for sale threads)
Engine mount/chassis repair
Solid Beam Mounts BACK IN PRODUCTION
Harness bars
Posted 25th Feb 2010 at 14:25
dented_vts

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Location: london

Registered: 23 Feb 2010

Posts: 440

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Post #13
"First off I'd suggest don't waste your money on aftermarket exhaust systems - the standard item is very good - save the money and spend it on cylinder head mods which will increase power throughout the range. As with other engines the trick is to get as much cylinder head flow as you can and then use as little cam as you need to avoid losing low rpm power." David Baker of Puma Race engines writing about the Mi16 engine.
Posted 25th Feb 2010 at 14:27
bobdylan_55

Seasoned Pro

Location: derby

Registered: 28 Mar 2009

Posts: 1,466

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Post #14
dented_vts wrote:
"First off I'd suggest don't waste your money on aftermarket exhaust systems - the standard item is very good - save the money and spend it on cylinder head mods which will increase power throughout the range. As with other engines the trick is to get as much cylinder head flow as you can and then use as little cam as you need to avoid losing low rpm power." David Baker of Puma Race engines writing about the Mi16 engine.


mi16 is not a gti6 engine. Id say leave the head alone, for the cost of some "simple" head work you could get a nice inlet cam and a remap and get much more power.

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Posted 25th Feb 2010 at 14:29
welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

Posts: 25,817

Status: Offline

Post #15
scary isn't it, just imagine how many potential tappers/valve droppers are out there, especially if the heads are skimmed too much!

dented_vts wrote:
cylinder head mods which will increase power throughout the range. As with other engines the trick is to get as much cylinder head flow as you can and then use as little cam as you need to avoid losing low rpm power." David Baker of Puma Race engines writing about the Mi16 engine.


oh dear Doh you didn't read what was posted above by a reputable engine builder then...


petert wrote:
dented_vts wrote:
You would be better off spending money having the head ported properly first, only then change the cams if you need to.


You're dreaming. The head already flows more than most "ported" other make heads. The limitation are the small camshafts.

You can run up to approx. 0.060" lift at TDC before entering the danger zone.


also, whilst bob is correct that the gti6 isn't an Mi16 engine, they flow just as well out of the box, most XU 16v heads will work well enough for mid 200's + without any work to them.

the key is the cams and bottom end.

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Posted 25th Feb 2010 at 14:35
dented_vts

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Location: london

Registered: 23 Feb 2010

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Post #16
Where does the 167bhp come from? The official figure i have seen for the XU10J4RS engine is 122kw (official EU power measuring unit) which is 163.6bhp.
Posted 25th Feb 2010 at 14:36
walker_texasranger

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Location: Sunny Retford

Registered: 26 Jan 2008

Posts: 2,502

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Post #17
I have got Kent PT80's in mine, the only other mods are Lightened Billet flywheel and crank pulley and a K&N. Standard exhaust/CAT and it made 180bhp when mapped with a lot better Torque curve, especially after 4000RPM. I was told at the time tht the PT80's (which are a fast road cam) were as lary as you can go without having to look at lifters etc due to clearance (if you wanted a proper job anyway)... HTH Smile

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Posted 25th Feb 2010 at 14:38
dented_vts

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Location: london

Registered: 23 Feb 2010

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Post #18
I don't doubt what was said just quoting an opinion of a race winning engine builder. I just wondered whether a ported big valve head would not produce as much not more power than a standard head on cams. My logic being that any original engine now is likely to quite tired and it may be a better use of money to have a head rebuilt to get the power gains than fit some cams and then still have to pay to get the head redone when it gives up.
Posted 25th Feb 2010 at 14:41
daveyboy

aka Jim Davey

Location: Southampton

Registered: 01 Oct 2007

Posts: 8,648

Status: Offline

Post #19
dented_vts wrote:
I don't doubt what was said just quoting an opinion of a race winning engine builder. I just wondered whether a ported big valve head would not produce as much not more power than a standard head on cams. My logic being that any original engine now is likely to quite tired and it may be a better use of money to have a head rebuilt to get the power gains than fit some cams and then still have to pay to get the head redone when it gives up.


Brett Simms (Longmans engine builder) told me this week that you can flow up to 280 bhp on standard size valves (they did) admittedly, rpm was circa 9K but it's possible. As for porting, he said just match the inlet manifolds and smooth the rough casting marks and leave the shape of the ports well alone, Peugeot did a pretty good job of the head already.

________________________________________

R H Davey Welding Supplies. I sell new and used welding equipment in the Hampshire area. I take on welding jobs in the evenings, ally casting repairs are one of my specialities but I can weld pretty much anything. PM me with your requirements.

Some of my services: (See my for sale threads)
Engine mount/chassis repair
Solid Beam Mounts BACK IN PRODUCTION
Harness bars
Posted 25th Feb 2010 at 15:40
welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

Posts: 25,817

Status: Offline

Post #20
dented_vts wrote:
Where does the 167bhp come from? The official figure i have seen for the XU10J4RS engine is 122kw (official EU power measuring unit) which is 163.6bhp.


everywehre I look, it says 167 bhp.

there's sod all to replace on these heads that would restrict power, they don't coke up like old 1950's engines.

Miles recently put his 250k mile Gti6 on the RR and got as close as you can get to standard power, an engine untouched bar servicing AFAIK.

________________________________________

need a part number? get on here - http://public.servicebox.peugeot.com

Bring on the Trumpets.

Posted 25th Feb 2010 at 19:33
dented_vts

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Location: london

Registered: 23 Feb 2010

Posts: 440

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Post #21
PSA would never have tested the engine in BHP- an out of date unit. The engine we have is 122kw when new. After 250k miles there would have been significant wear. If you test the compression of an engine when new and then when its done 100k miles you will notice the compression is lower and therefore it is not possible for an engine to develop the original power figure. If the 250k engine made the same power as a new engine it would mean no engine wear had taken place, that is impossible.

The ONLY means of measuring the output of an engine is via an engine dyno. RR values should be used for relative comparison only- ie take a reading before and after modification to see if it has made any difference. You can only guess at the flywheel power from a measure of brake power at the wheels. I guess a new standard engine should make about 135-140 at the wheels. I plan on having mine on a power run to see how far off original performance it is.
Posted 26th Feb 2010 at 21:24
dented_vts

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Location: london

Registered: 23 Feb 2010

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Post #22
Actually as to date and legal requirement might not be totally accurate but would definitely not be BHP as that is not an SI recognised unit.
Posted 25th Feb 2010 at 19:55
dented_vts

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Location: london

Registered: 23 Feb 2010

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Post #23
PS as a unit rendered obsolete in 1992 by directives though so that leaves only KW.

What BHP at the wheels figures have people achieved with standard engines?
Posted 25th Feb 2010 at 19:59
welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

Posts: 25,817

Status: Offline

Post #24
dented_vts wrote:
If you test the compression of an engine when new and then when its done 100k miles you will notice the compression is lower and therefore it is not possible for an engine to develop the original power figure.


care to explain all the thousands of cared for vehicles out there producing book bhp then?

________________________________________

need a part number? get on here - http://public.servicebox.peugeot.com

Bring on the Trumpets.

Posted 25th Feb 2010 at 20:12
dented_vts

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Location: london

Registered: 23 Feb 2010

Posts: 440

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Post #25
Compression decreases decreases with mileage, i therefore have to conclude they produce less power as a result. How else do you get power to the crank?
Manufacturer power figures will be calculated with a perfect engine in a lab in ideal conditions with a all perfectly run in parts and new exhaust and lab spec fuel (prob 100RON). You cant possibly expect a 100k mile engine to produce that can you?

You speak of these old engines producing the original claimed power but how do you know if they do without removing them to test.

On one trip to a rolling road I ran in 3rd gear then 4th then 5th- all gave a different
figures! Completely meaningless values- according to the machine the transmission losses were different each time!

I used to have a mk2 16 golf- a car people say gets better with age etc and can produce original power. Hmm, high lift cams, vernier pulley, new seals fuel pump genuine exhaust etc etc with 75k on the clock still only made 122 at the wheels- ie 140bhp fly. VW technical states power losses via transmission is 15%. Original claimed figure in magazines etc 139bhp (actual figure 102kw a bit less than 137bhp or 139PS).

Posted 25th Feb 2010 at 20:32

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