Hi Comp pistons and other vts tuning

[diy_gti]

Hi, there quick bit on the car,

Citroen ax with VTS engine conversion, mods already done 4-2-1 mani, magnex system, viper ind kit (soon to be bmc) adj fpr (soon to be 4.5 gmc special - i've learnt the error of my ways with power boost valves so lets move on.) oh and the remap. it made 148hp at the fly.

ok the situation i'm facing here is that from either running too lean before the map or the grit that somehow got in to the viper, i now have a smokey engine, assuming its the rings after a little digging.

i'm now looking to rebuild the engine again as it has to come out, (pause), again. so i'm looking into hi comp pistons and definately having cams (newmans or 708's - whichever is cheaper to buy when i need them) oh also a shot of nos with help of a controller. any other advice would be welcone!

anyway the question is, which pistons have the best rep when used with either of the cams above, plus what extra work might need doing? i know the vaux 1.6 16v has a prob with its hydraulic lifters coping at high revs knocking it down a gear causing valve and piston to get intimate. with similar spec. i've looked at wiseco pistons (good value altho 11.5:1 they do come with h sect rods at a decent price <£600) also IAPEL pistons, so does anyone know of problems with clearance?

TA, Chris

[Ryan]

708s wont need soild lifters due to the spec of the cam so thats not a problem, the high comps should give better low-mid torque.

both the pistons you mentioned have good rep, and wont clash with 708s. the 708s duration is ok to run on std pistons tbh!

gmc/qep for pistons.

[Toad]

I love these RR figures... ;)

EDIT: It wouldn't have been running lean before the map, as you haven't done anything to make it run lean. The stock ECU will always "err" on the side of safety = rich. ...Unless in some way you managed to restrict the fuel with FPR - Never seen that one before! ;)

As already mentioned by Ryan, you don't need to change the pistons with camshafts in the mild region like 708s.

[bullit]

I love these RR figures... ;)

EDIT: It wouldn't have been running lean before the map, as you haven't done anything to make it run lean. The stock ECU will always "err" on the side of safety = rich. ...Unless in some way you managed to restrict the fuel with FPR - Never seen that one before! ;)

As already mentioned by Ryan, you don't need to change the pistons with camshafts in the mild region like 708s.

in wasnt gonna say anything lol.

see ryan mentioned about the torque pistons giive from compression etc. this is what i meant about gains instead of headwork

edit- the other error was mapping without putting cams in. or dont do a toad and go for standolone now ;)

[Toad]

I understand. But you can't just increase the compression ratio mahoosively, or it will just pre-detonate. Skimming the head will increase the compression too, giving a bigger band effectively.

Ryan, tell us more about these high comp pistons.

[bullit]

I understand. But you can't just increase the compression ratio mahoosively, or it will just pre-detonate. Skimming the head will increase the compression too, giving a bigger band effectively.

Ryan, tell us more about these high comp pistons.

and wheres josh lol

edit. also woosners are quite popular, sure gmc do them aswell

[Toad]

Hehe, just read your EDIT. Shit, if i only I knew what I was doing back then! I still don't know what the fcuk I'm doing actually...

[bullit]

lol. you do. its when you start you dont see how far your gonna end up etc

you must have been on the wrong forums ;)

[diy_gti]

[QUOTE=Toad;1422523]I love these RR figures... ;)

EDIT: It wouldn't have been running lean before the map, as you haven't done anything to make it run lean. The stock ECU will always "err" on the side of safety = rich. ...Unless in some way you managed to restrict the fuel with FPR - Never seen that one before! ;) QUOTE]

Figures are accurate, lets leave it at that. it WAS running lean, popping banging and ressistant at top end to accelerate, and the emmissions were the proving point. so as you mentioned the FPR was obv to blame - (power boost valve), once tweaked and remapped it was beautiful to drive. until now that is.

originally i was going to run the engine as it was, this current problem has provoked the changes, if i'm taking the engine out and stripping it down then it's worth my while improving on what i've got, so thats why i had the re map done. don't mind paying again for it once rebuilt because of above reasons and the extra gains it should make! plus i get it done at a good price cos i give all my work on my golf to the place which does the mapping! which amounts to more than the ax budget. for the time being anyway.

So, back on point, the opinion so far is, save the money on pistons, skim the head to raise compression what about nos? any upgrades i should be thinking of like better rings or any other parts? only looking for a MAX 50 shot if that, just something when i need it!

[Toad]

Not unless you're not telling my about something... 148 bhp - no chance in hell dood.

I can't comment about the nitrous, it's not something I know much about. I guess the first thing would be to find out what's up with the engine really. If it was running lean for a while, there's a good chance the pistons are shagged...

With all the mods you've already done, plus a set of 708s, you'd be looking at about 150 "genuine" horses. So if you've got 148 of them already, there won't be much point in getting them...

[bullit]

Not unless you're not telling my about something... 148 bhp - no chance in hell dood.

I can't comment about the nitrous, it's not something I know much about. I guess the first thing would be to find out what's up with the engine really. If it was running lean for a while, there's a good chance the pistons are shagged...

With all the mods you've already done, plus a set of 708s, you'd be looking at about 150 "genuine" horses. So if you've got 148 of them already, there won't be much point in getting them...

unless he will get 170 ;)

[Toad]

Yeah... We had a chap on PGTi come in one time, claiming around 165 - 170. Still on stock camshafts and intake. Makes you wonder. :)

[diy_gti]

Well, for some years now, over several rolling roads the same cars tested or similar spec cars mild mods -std engine just filter and (ax fitment) magnex exhaust or similar on the ax conversions- all generally make around 140-143bhp as i said over several rolling roads, not shoddy establishments

quite reputable ones infact, including Northampton motorsport & Stealth Racing (specialist VW tuners, highly regarded in the dub world as the prophets of 20vt tuning, and recommended by dta for mapping their systems cos of the reputaion of Vince chief engineer - hence why this is where i get all my mapping work done and majority of the work on my golf too) also where and whom i lay implicite trust to draw the absolute most out of the car i give them!

based on this i'm thinking that the increase in fuel pressure and remap on my ax is worth the 148bhp. also toe to toe spats with 2.2 prelude engined civic, escort RS turbo's, Skoda Fabia VRS have shown the power produced is up in that region, obviously weight is an issue. But it sure feels quicker to 100 than my VR6.

what do the saxos tend to put out with filter and exhausts then? most i've come across all seem to be there or there abouts! the addition of cams is obviously going to have an impact somewhere logic would say an increase of top end power thus the suggestion of 160 - 170 bhp!

why all the Smarmy comments trying to put people down within their first few posts, when asking what i would perceive to be a justified question.

I appreciate all the positive responses here by the way and anticipate a fully constructive answer/discussion to commence.

Thanks again.

[Joesnow]

I don’t think anyone’s trying to be smarmy… just there’s no way you can get an accurate flywheel figure from a chassis dyno, however reputable the company is. If they tell you they can… they aren’t very reputable at all… it’s all a big guesstimate.

The only true way of calculating an accurate flywheel reading is by having your engine tested on an accurate engine dyno

It could very well be 148bhp… but I would never quote it as that as it’s just been estimated. I wouldn’t worry about a figure for power output… as long as you know it goes well.

I think chassis dynos are only really good for mapping and seeing if any mods make a difference or not… not really good for comparing two different cars or calculating flywheel figures.

It will give you some indication but I think 148 for those mods seems a bit high… some people cant even get that with higher lift and longer duration cams…having said that they will have had there’s guesstimated too!

To get a genuine 160-170 break I think you would need throttle bodies

[bullit]

only playing mate, and toad has the drying sense of humour

[Toad]

Peace :ying:

[ihavealargeone]

Peace :ying:

but it wont make that power ;)

[vtr130]

708s wont need soild lifters due to the spec of the cam so thats not a problem, the high comps should give better low-mid torque.

both the pistons you mentioned have good rep, and wont clash with 708s. the 708s duration is ok to run on std pistons tbh!

gmc/qep for pistons.

My pistons and valves were clashing a tiny bit with 708's and standard pistons. You can see the marks.

Check my progress thread for a n/a rebuild mate ;)

[Ryan]

My pistons and valves were clashing a tiny bit with 708's and standard pistons. You can see the marks.

Check my progress thread for a n/a rebuild mate ;)

what way was your timing set up?

as yours would be the only persons car ive heard of with that happening.

high revving cunt :P

[vtr130]

Well i didnt expect it to happen, but reving to 8k on standard pistons could have caused this ;) Nd my driving style... lol

But i think with 809's and hi comp pistons the clearance is going to by 25thou so i should be ok ;)

[Ryan]

Well i didnt expect it to happen, but reving to 8k on standard pistons could have caused this ;) Nd my driving style... lol

But i think with 809's and hi comp pistons the clearance is going to by 25thou so i should be ok ;)

erm 8k and your driving would prob explain it, slight clipping isnt a huge problem, only full on smashing of them into each other lool

[Toad]

GMC recommended I uprated my springs, as the bigger valves will weigh more etc, etc... I'll look into this one!

I don't know what's going on internally at the moment, but my car has gone skitzo. The past week it's driven better than I can ever remember. I suppose I did get the exhaust sorted the other week... Anyway, has anyone else noticed their car performing differently every so often? Especially those who've had a re-map from Chipwizards...

[diy_gti]

ok cheers guys, just seemed it was "bring the newbie down week" on here!

not any group buys going on at the mom or the near future that anyone knows of for cat cams or the newmans are there?

[bullit]

ok cheers guys, just seemed it was "bring the newbie down week" on here!

not any group buys going on at the mom or the near future that anyone knows of for cat cams or the newmans are there?

the comment would have been the same to an established member mate as we all know what figues go around on tuned saxos, gti etc

anyway cams. dont think any grp buys at the min but kam racing sell them for 350 delivered for cats iirc ;)