Turbo cam choice - from experienced users please!

[dan1300r]

Currently my Polo Breadbin consists of the following platform (keeping it simple): 1341 bottom, standard valve size ported head, ported g40 inlet manifold, original G40 cam, DTA S40 management, G60 injectors, Golf 1.8 throttle body for TP Switch function.... It's Full blend Lader is giving hideous boost at 1800rpm and is walloping tyres and driveshafts even with a boost/vacuum controller + dump valve setup to dump some boost low down. These Laders seem to take some managing without the original bypass/throttle body.. Anyway I prefer the progressive spool up of turbo setups so I now have my K04 bolted up and am scratching my head at cam choices.. I know big turbos on little motors come with big lag hence why I've kept the G40 inlet manifold/std valve size - I want to keep fast low down airflow to reduce lag. I'm not in the budget for building hybrid turbos so will have to make do with the K04 I found in the parts bin. Some say GT cam with big turbo will spool it up quick and then die at 4500.. I don't know.. Will the G40 cam further exaggerate this?? I hear that n/a cams are best (like GT) I also have on the shelf a 1043cc std cam.. Anyone used one of these...?? It's a minefield! I've probably opened a can of worms now! Would be nice to hear what you lot have to say.. Thanks in advance.

[Andy]

Out of all the OEM cams, the Polo GT (3F engine) is the best to use. With a K03 though it'll give a 1500-4500rpm powerband, though I've mapped a K03'd car with a 3F cam that had more like a 2500-5500rpm band but it had a lot of headwork done and machined-down NZ pistons so various engine characteristics had changed as a result.

I'd try a 3F cam with the K04, but be prepared to go for something longer duration. Piper do a 254°/254° that might be a good compromise. G40 original cams are crap with turbos, and the stock 1043cc and 1272cc SPI cams are pretty useless too - choke up way too early. 3F cam is a good match to a bigger turbo like a T25.

[dan1300r]

Aah I spotted the piper 254/254 and raised an eyebrow... At a guess, where do you suppose my power range would be? Also looked at the Shrick 264/260 and 268/264... I'm somewhat tempted by the 264/260 if I can't get hold of a 3f.. I was in thinking that with the 1341 bottom and merely cleaned/smoothed/shaped (not so much opened up) ports to matched inlet I should have good fast low down venturi for good spool up, but also thinking that with the smaller inlet manifold that it may be pointless going up to the 268 down to not having the best flow characteristics high RPM thus not getting the full potential from this cam.. How does this sound??

[polo classic]

Loads of info here

http://www.g-laderseite.de/forum/viewtopic.php?t=2121

http://www.g-laderseite.de/forum/viewtopic.php?t=12519

Hows your german

[Andy]

It was the G-laderseite boys wanking over 3F cams that made me try one after finding the PY, AAV and PSD '1341' cams were shite with a turbo. The K03 needs a lairier cam though, but a 3F item seems to work well with a bigger turbo.

[dan1300r]

Great stuff, I will try and find a 3F cam first port of call, they don't seem to be popping up on ebay.de this week, will have to keep an eye out or if anyone has one?.. For now, I'll have to see how it goes with the 196deg std cam that came from a carbed 1043 HZ, May be better than we think with a big turbo? Not even going to try the G40 cam.. I'm also using a thin ish 1mm head gasket so with the higher CR (aprox 8.3-1?) it may not be too bad off boost either.. Thanks for the input.

[dan1300r]

I must add that I'm not looking for big HP, more of a driveable car so I'm thinking that with the 'useless' n/a cam this may help? (Andy)... Maybe it will boost too hard and too low like the G Lader did? I kind of expect with this set up it may make a lot of torque lower down and may peak circa 180hp at 5500.. I know it's a stab in the dark but I will post the dyno results once it's set up.. Will be a couple of months yet..

[jez1272gt]

This makes me wonder what cam would be best for a 1341, p&p BVH, 51mm TB etc etc with GT25 ... i have a shrick turbo cam in at the moment, anyone any experience in what the difference is like between that and the 3f GT unit anyone?

[Andy]

What GT25 variant do you have?

Yoof runs the GT2554R, seems to give 4-7k powerband with a 268° cam which is great on track - would be interesting to try it with a 3F cam and see if that lowers the powerband at all.

[jez1272gt]

i have a gt2554R as well... i'll be starting with the shrick cam but wondered if anyone had any experience with both on a high spec build. i need to get the thing running before i worry about which is better really lol...  interested to know though..

[Ä‘uro]

Just a quick one; on which rpm 2554R start to spool ?

Cheers

[dan1300r]

I now have a dyno result: Ran the 196deg HZ cam with a K04-015 turbo (the one with the small/K03 hot side) at 1.2 bar and got 218ftlb torque at 3100rpm and 172bhp @ 5100rpm (not too far from my 180@5500 prediction). Tried to add another few PSI and the power fell right off, so the cam is choking it up after here but what I do have is boost starting at 2200rpm and holding full boost from 3500rpm right through to red. No lag is noticeable, it drives like an with a nice straight line on the graph. Lovely silky drive. I still want to see what the GT cam does.. Additionally, does anyone know how much better a GT inlet manifold will be over a ported G40 one? I know it may help ultimate HP but I'm worried the extra flow may increase lag?

[Yoof]

Nice Dan- what boost pressure is that at?

Boost low down is good, but the gearbox really won't thank you 

[dan1300r]

I have attached dyno printouts for my breadbin as it has progressed, I have added notes on each as to the platform I have used, I have a drop-off and pick-up on the GT cam and inlet run due to wheelspin, not a flatspot.

[dan1300r]

I now have a dyno result: Ran the 196deg HZ cam with a K04-015 turbo (the one with the small/K03 hot side) at 1.2 bar and got 218ftlb torque at 3100rpm and 172bhp @ 5100rpm (not too far from my 180@5500 prediction). Tried to add another few PSI and the power fell right off, so the cam is choking it up after here but what I do have is boost starting at 2200rpm and holding full boost from 3500rpm right through to red. No lag is noticeable, it drives like an with a nice straight line on the graph. Lovely silky drive. I still want to see what the GT cam does.. Additionally, does anyone know how much better a GT inlet manifold will be over a ported G40 one? I know it may help ultimate HP but I'm worried the extra flow may increase lag?

I hope my memory served me well when I wrote this down! I have now posted my dyno results - I wrote this from memory as I remembered my dyno man telling me over the phone... All will see how my memory served me.. I don't like to tell lies if I can help myself