Light weight engine build - Engines Forum - Peugeot 306 GTi-6 & Rallye Owners Club

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Subject: Light weight engine build

simonjames

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Location: Whitland S.Wales

Registered: 23 Nov 2004

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Post #1

Well with me selling my low comp bottom end to birk due to funds running out Sad

i've had to weigh a std 6 bare block and with it coming in at 44kg it got me thinking (yeah i know it dont happen much) would i be able to build a light weight set up using an xu7 block d-turbo crank then use low comp forged pistons and rods.

would the xu7 block be the same height as an xu10?

or has someone made a simailar set up using oe pistons/rods i.e 1.9 205 pistons and mi rods

When i did the engine conversion on my xsi from an xu7 (was wrongly fitted)with a 5 speed to an xu10j4rs with a 6speed i noticed the car under steer alot compared to before, i put it down to the extra weight in the box with the exra gear but im thinking now it may well be the block as well Hmm

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Posted 5th Feb 2010 at 16:33

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ryangti6

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Location: Pontypool

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Post #2

This is pretty much what I am doing although I will be staying Na.

I'm pretty sure when I measured the xu7 block it was ~10mm shorter, this was just measuring the face for the sump to mount to the deck.

Also my xu7 weighs about 27kg bare, no crank,pistons or rods etc.

The extra weight on the conversion you mentioned would not of helped understeer but I expect the extra power was playing a big part too.

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Posted 5th Feb 2010 at 17:05

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simonjames

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Location: Whitland S.Wales

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Post #3

Yeah i think it was a combination of everything to be honest after fitting the 6 eng/box the car didnt feel as quick in the bends

10mm shorter face to face but i see on the 6 block the mains are lower than the sump face is it the same on the xu7?

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Posted 5th Feb 2010 at 17:16

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welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

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Post #4

from the crank centreline to the block-head mating face they are 224.5mm, 11.5 shorter than an iron block which is 235mm from what I can find.

hence the use of 143mm conrods on an 88mm stroke (pistons are about 37.12mm compression height)

you could use the 1.9 Mi16 or the Diesel turbo crank, both are 88mm stroke, as is the 1.9 8 valve.

if you use the XU7 block I would keep the liners as they tend to be in good condition, use the gti6 head as it has bigger ports (or get the XU7 one worked over)

use a 1.9 crank, 1.9 Mi16 pattern rods and pistons.

ryan, was that 27kg including the liners?

You would need to weigh them as well to give a fair comparison to a bare iron block.

IIRC sandy said that the bare XU7JP4 engine weighed about the same as a 1.9 8 valve, 100 Kilos give or take a few.

The gti6 box weighs 5 kilos more than a 5 speed unit.

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Posted 5th Feb 2010 at 17:44

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simonjames

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Location: Whitland S.Wales

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Post #5

Cheers mei thats a good bit of info

but if i wanted to build a low comp unit (s/c'd application) i'd need to use forged low comp 1.9 205/309 rods/pistons yeah?

i have a d-turbo crank and i know for a xu7 Smile

so it would then just be the rods/pistons i'd need to source

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Posted 5th Feb 2010 at 18:11

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mxcrazy

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Location: hastings

Registered: 22 Jun 2009

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Post #6

simonjames wrote:

so it would then just be the rods/pistons i'd need to source

bearing in mind 205/309 1.9 are 8v.

As welshpug says a set of pistons/rod for mi16 1.9 boosted application.

Posted 5th Feb 2010 at 18:28

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simonjames

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Location: Whitland S.Wales

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Post #7

Would the bore be ok in the xu7 liners?

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Posted 5th Feb 2010 at 18:30

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welshpug!

Capt Pedantic

Location: Bigend, Wales.

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Post #8

yeah, best to get something primarily designed for the Mi16 and make sure the valve cutouts are ok, they should be though as the Mi16 can accept fairly high lifts as standard.

all the alloy XU's are 83mm bore, so yes perfectly fine to use.

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Posted 5th Feb 2010 at 18:33

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simonjames

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Post #9

top job

shopping list

low comp Mi16 rod/pistons

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Posted 5th Feb 2010 at 18:33

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welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

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Post #10

the only thing I think you might struggle with is mounting the charger bracket, but I havent seen what the a/c XU7 auxillary /engine mount bracket looks like, easy enough to mock up and get the plate adapted if needed, potentially would need a different length belt.

I have the non-a/c version here and its in 2 separate pieces.

I might weigh my block later today if I get chance.

Some people seem to have struggled a little with the breathers, but they weren't running anything like the standard routing (or an XU7 block in one case) which works fine, I wouldn't be worried about it myself.

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Posted 5th Feb 2010 at 18:54

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simonjames

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Post #11

im sure the aux bracket/cradle bolt points are same?

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Posted 5th Feb 2010 at 18:57

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adam b

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Post #12

For reference an RS engine complete with a non a/c aux setup and no starter + wiring (but with clutch, fly, oil cooler, most water pipes) comes in at just over 160kg.

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Posted 5th Feb 2010 at 19:02

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ryangti6

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Post #13

Welshpug- That weight was with liners still in place.

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Posted 5th Feb 2010 at 21:35

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welshpug!

Capt Pedantic

Location: Bigend, Wales.

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Post #14

great thanks, a fair difference at 17 kilos Smile

crank I would think weighs around the same, pistons and rods potentially a fair amount lighter.

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Posted 5th Feb 2010 at 21:43

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allanallen

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Location: Buxton

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Post #15

I'd be tempted to go for crank located rods rather than the floating mi ones. Perhaps some 8 valve rods and modify the mi pistons to suit?
Having seen proof that this drastically helps oil surge problems on mi's it seems silly to use the piston located set-up. You may end up with a light weight,high powered oil surge monster!

Allan

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Posted 5th Feb 2010 at 23:19

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welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

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Post #16

might be something to look at..

But isnt the 2.0 MI16 crank located? they still suffer just not as bad (span a rod on my RFY engined ZX on a v-tight fast l/h bend!)

However the crank located gti6 doesn't seem to suffer at all.

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Posted 5th Feb 2010 at 23:31

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adam b

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Post #17

I thought the oil pressure problem was due to the head design? Dry Sump FTW Big grin

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Posted 5th Feb 2010 at 23:34

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buzzbrightyear

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Post #18

lol, how the bloody hell do you know all this technical shit about these cars, and also how the bloody hell do you remember it all.

welshpug! wrote:

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Posted 5th Feb 2010 at 23:42

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welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

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Post #19

reading forums for countless hours on end (i.e being unemployed) and knowing where to find that kind of information if I so happen to call upon it, I might not know what you ask but I'll sure try and find it Big grin

amusingly as yet haven't built a pug engine but have taken a few apart and done quite a few headgaskets.

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Posted 5th Feb 2010 at 23:50

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welshpug!

Capt Pedantic

Location: Bigend, Wales.

Registered: 27 Mar 2007

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Post #20

adam b wrote:

I thought the oil pressure problem was due to the head design? Dry sump FTW Big grin

quite

PSOOC member in stoke has a carbed 1.9 MI16 205 with a nice bottom end + stock head and a set of cams for 200+ bhp, and a dry sump, hasn't gone bang yet but ask him about panel gaps, Blue Haddock likes bringing that up with him LOL

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Posted 5th Feb 2010 at 23:52

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buzzbrightyear

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Post #21

well, i dont want to suck your dick or anything, but i have to say that your one of the most helpful and knowledgable people on here.
thanks mate for helping me and others out countless times!!
andy

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Posted 5th Feb 2010 at 23:53

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allanallen

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Location: Buxton

Registered: 01 May 2007

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Post #22

adam b wrote:

I thought the oil pressure problem was due to the head design? Dry Sump FTW Big grin

Can of worms Whistle

Yeah 2.0 mi is crank located, they don't suffer oil surge anywhere near as bad as the 1.9 imo. I don't want to get into a debate of weather or not the piston located rods do cause oil issues as its been done to death and I have no experience in testing the two setups .......but knowing that they COULD cause issues I would personally steer clear of using the piston located set up.
If I ever have to rebuild my mi it will be having 8v rods.

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Posted 6th Feb 2010 at 00:06

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adam b

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Post #23

Yeah I spent a long time looking into the issue for Jonmurgie before we nearly built his dry sump system. Shame funds didn't quite allow it - all the parts were in place and created. There was a guy in evesham with a dry sump'd Mi16 about 5 years ago. Was quite a bit of kit, but not as nice as his Lotus Sunbeam.

Hey hum!

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Posted 6th Feb 2010 at 00:43

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