No substitute for cubic inches?

R

Renault17

Active member
Fellow Frogger
Joined
May 11, 2001
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314
Location
New Zealand
Hi Guys,
I have posted stuff before about hotting up an r17r18 motor. Generally speaking, the replies have come back with the following suggestions;
compression ratio increase
twin sidraughts
extractors
camshaft grind
balance and blueprint (if money allows)
bit of headwork if possible
And if course generally replace worn out bits,re-ring, bearings etc

My question is this- how easy or wise is it to increase the capacity on the (843) 1647cc motor? Being a wet-sleeve motor, and if you are going to the cost of replacing the pistons, why not get bigger ones if std replacements are hard to come by?
How big can you go before the liners get too thin, reliability/integrity is compromised? Is this a logical progression for more grunt- the only other way I can think of stroking the motor- is with a different (very expensive) crankshaft isn't it?

I was thinking that if I could get an increase in capacity to close to 1800cc, with the twin sidedraughts that I already have, and extractors, cam grind and balance everything that it would make a good, strong motor. I have finally had the go ahead to spend some money on it(from the missus! head_ban so am trying to suss out sources for parts etc- ie so if I am going to be hunting out forged pistons and could get a 'free' increase in capacity it'd be silly not to take it...

Another thing, this motor the camshaft had specs of (I think) 72, 32. Will this be a hot enough cam for what I am trying to do? The aim is around 140 odd hp, and the car is used relatively infrequently...
My apolgies if some of this seems like rehashing earlier posts- it's just that I don't think I got a definitive answer on the capacity issue.. cheers!

Cheers Ben
 
Sounds Interesting Ben

I reckon try get the Sleeves bored close to 1800 get the crank nitride, pistons n rods forged, clean ports up a bit, bigger stainless valves, tight valve springs. Roller rocker top end if possible, Chuck an EFi set up on it, running off a Motec ECU.

Ball Bearing High flowed Turbo running 17PSI.
Find a adequate box, if Reno offers such a thing, then hit the Tarmac telling the world that your the poorest man in the southern hemisphere.

Its what I'm planing on doing one day. tongue

Ya just Can't beat forced induction.
 
The fitting of larger bore liners and pistons will be an expensive experience. I am currently trying to do it on the cheap without buying the megabuck Mecaparts kit. And all this for only 200 cc.Not a good return for the effort and dollars. I am adapting 205 GTI liners and have not found pistons yet. It is far from a direct fit, with turning and milling of the liners and block to achieve 84mm bore,and with them bored out 1 mm a total of 1860 cc.
For you I believe the cost of custom stainless valves of 42 and 37 mm will cost $50 each, and with all the various new parts, headwork, cam, valvesprings, standard piston and sleeve, carbs, manifolds, extractors and system, and balancing will cost a minimum of $3000, without an additional $1000 for 200 miserable ccs. This is not original but: HP costs dollars, how fast do you want to go? You should be able to get your 145 HP with 1647CC with the "standard" mods mentioned. To answer your cam question, you will need at least 400 thou lift at the valve with the duration mentioned, or the Renault way to power, with a lot more duration, but no low down torque or power, but plenty above 4500 rpm.

Alan.
 
Is the 843 the crossflow (R16TS/TX) version? If it is, it's a bloody good engine in terms of durability, breathing, cooling etc so I wouldn't want to mess with the standard sleeves and pistons, or play with the head too much. Just go Turbo!
 
I found this on the G-Forum site, re a 4CV special:
"I use a R10 gearbox to which a 16TS motor is fitted. The engine has been modified in the following way. Wet liners come from a 1800 Alfa and machined to fit in the block which was also machined to accept the wet liners. Pistons come from a BMW 320i (I think M60 pistons). The cam is a RA5. The head has been ported, but I still use the original size valves. The compression ratio is 10.4 : 1. I also use two 45 Weber's and a 4/2/1 custom made exhaust manifold."
Might be of some use.
 
If you want reliability and extra grunt with minimum outlay forced induction is the way to go, in fact it really should be the first step in all performance mods no far how you go.
 
Mine had 165hp at the rear wheels... yes, rear wheels, it was in a sports car.

It was still standard bore then, had a Cosworth A6 cam grind, a little work on the head, including .060" off it, Repco SR454 pistons (made originally for the Renault Australia rally cars), twin 45mm Webers.

I'd go for boring .030" and have some pistons made by JP in Adelaide to the crown design of the SR454. They will be lighter and have better rings than Repco supply, and you won't have to buy liners.

You should then get your 140hp with the normal TS head (simply scalloped out around the inlet valve and somewhat polished... do not make it totally hemispherical) and a better inlet manifold. You don't need to go for multiple carbies, though for road use I'd come back a tad on the cam (from the A6) and try to work a way to fit two 1.75" SUs (ex-Austin 1800... droves of them around!) to give flexibility and economy with your 140hp.
 
Ive got an A6 Waggott cam in my R10 with a Virage 1.4 and twin 40 DCOE Webers.. and its pretty easy to drive through heavy traffic, and if I want to I can still get 40mpg out of it. Dunno how, but it can get it. :)
 
peabody:
If you want reliability and extra grunt with minimum outlay forced induction is the way to go, in fact it really should be the first step in all performance mods no matter far how you go.
Click to expand...
I'm not so sure about this...

Modern bearings are much better than the old days, when supercharging was said to be more reliable than other methods of hotting up engines.

Superchargers aren't cheap, turbochargers add their own complications, both are immediately obvious when a copper opens the bonnet.
 
Hi Guys,
thanks for that- Alan- the reason I was wondering about an increase in capacity was that I had my motor dynoed (and I realise that there are dyno's and there are dyno's....) but it only had 92hp with the twin 40mm sidedraughts and exhaust already done. So I was figuring that more than just a head, compression and a balance etc would be required to hit the 140-150hp mark. I'll be stoked if I can reach that with less- just didn't want to overestimate what was possible that's all.

Interestingly enough, since this post, I have spoken to a renault guy in Ak in the last few days- he has raced speedway cars for years- using renault motors, and has done very well with it and knows his stuff, anyway....

He suggested that the best place to start was to take the head to a head shop and get it flow tested- and that they will be able to tell me what capability the motor has and what mods should be done to get the power i.e. they will be able to say- yes, this motor has a good flow rating - should be capable of around 180hp- with these mods- compression ratio increase, this cam, these head alterations etc etc.or alternatively (and not likely, given reno's typically good flowing heads) no, this will flow no more than 110hp- you are kidding yourself to develop this motor any further.

Has anyone else taken this pathway to modifications? I am wary of getting ripped off - but at least this way you'd have something to quantify your modifications against- ie if you do what they say and it doesn't ....then you have a some sort of comeback.

This same guy was telling me that they spent over $1500 NZ$ on a head for a race motor- but he felt it was money well spent.

I'd be interested to hear your thoughts.

Cheers Ben

ps Ash a turbo at this stage is NOT an option(altho heaps of fun!)- I want it to look original. Besides that is what my R18 turbo head_ban and fuego are for!
 
I had one of my heads flowed many years ago. The results were very good. The V8 type guy raved about it, and then started talking about 600 thou valve lift, a near impossible engineering feat, but quite common on V8s. Without going through all the figures, basically it flows as follows.
Inlet 450 thou 180HP at7620 rpm
500 thou 184HP 7810rpm
550 thou 188HP 7985rpm
600 thou 190HP 8080rpm
The exhaust flows about 86% of the inlet up to 200 thou and then around 78% up to 600 thou. Of course the exhaust does not have to flow the same as the inlet as the gas is expelled by the piston. Ideally the exhaust port should be less wide and a little taller for best laminar flow, as the air breaks away from the walls and causes eddys as the port opens out too quickly. A Fuego Turbo head looks to have better port shape, but I have not tested this, and besides they are very rare in AUS.
I run 34mm chokes in my sidedrafts, inlet ports 37mm, inlet valves 42mm Ex 37mm and only a basic clean up of the ports, as most people hog out the bottom of the port to make it larger, but all the flow is at the top.
A bit long winded, but I am quite passionate about these beaut little motors.
Alan.
 
Hi Alan,
thanks for those figures, was that with the 807-10 (large valve) head? As I am using the 843 motor and head-do you know if aside from valve sizes if there are any differences in head design- i.e does that head flow as well as the 807-10 head?

And were those numbers that the 'head guy' gave you using a std head or one that had already been ported?
Cheers for the advice.

Ben
 
It was an 807 crossflow type head that originally had 40mm valves. Is yours a 20 TL crossflow motor?
If so the head is similar, but I have not looked closely at one. The head was ported, but not in a major way as they are quite good standard. The valves were stainless, with the stems thinned down where they go through the ports. The motor amazingly still survives today in a yellow Dauphine G, over 10 years without a rebuild after many hillclimbs etc.
Alan.
 
You don't seem to take any notice of my post...

That was an engine that was built and ran without any problems for a couple of years of serious racing.

It was easily done, with only the pistons non-standard.

Don't bother with flowing the head, and keep your 40mm Webers too if you like. The key to the power was the flame pattern created with those pistons.
 
I agree with Ray, with your Webers already in place there is really only compression and cam to make up the majority of the power with the percentage gain on the head minimal. A set of 4 into 1 extractors, 34" long 1 1/2" inside diam.and a 2 1/4" system will also help, plus some time on the dyno.
Alan.
 
Ray Bell:
Mine had 165hp at the rear wheels... yes, rear wheels, it was in a sports car.

It was still standard bore then, had a Cosworth A6 cam grind, a little work on the head, including .060" off it, Repco SR454 pistons (made originally for the Renault Australia rally cars), twin 45mm Webers.
Click to expand...
Are you sure that that dyno was accurate Ray?
165hp at the rear wheels is atleast 200hp at the flywheel, which is more than wild versions of the same engine in Europe got. Renault had to fit a 16V head when they wanted to get that kind of power output. They usually had to bore the engine out to 1796cc to get that kind of output in 8V form.

Dave
 
Hi Guys ,
thanks for the replies.

Alan- so (if i understand you correctly..) the cam grind I need will have to provide 400" lift to be able to flow enough air for around 140hp?

Ray- so only those pistons plus cam etc were the really 'trick' bits on the motor- and it made 200hp! I would have thought 160-170hp (flywheel) was their upper limits for reliability/performance.

I have spoken with the guy that did the dyno work and have come up with the following plan of attack.

Use the spare motor from another fuego GTS that I have - so my other car can stay on the road.

Take the head in and get him to clean it up, match ported to the dellortos, and gas flow it. Std valves, inserts etc will be used.

Once we know what it will flow the cam grind will be selected. (A6, or cosworth- are the only grinds I have had mentioned by number thus far..)

I have (hopefully !) secured a new set of pistons and liners. These and the conrods, crank, flywheel and pressure plate will be balanced.

Then re-instal with new rings, bearings etc and a bit of time on the dyno to ensure it all goes together.

Cheers Ben
ps this'll take a couple of months- for interests sake I'll let you know the outcome of the changes on the dyno.

pss A final question- is it possible for me to try to 'dial' the cam in or not- or does it only apply to OHC motors?
 
Probably the most important part of what I had was the piston crown shape... and the way it integrated with the head... and the fact that the head wasn't fully 'hemisphered' but was only relieved around the inlet valve.

I know you won't believe me, but it's true. You don't need new pistons and liners, you just need those pistons... or pistons made just like them.

The A6 is a Cosworth grind... a mid-sixties full race grind as used in things like F2 etc.

And yes, it would have to have been close to 200bhp at the flywheel, and it never gave any trouble whatsoever.
 
Ray Bell:
Probably the most important part of what I had was the piston crown shape... and the way it integrated with the head... and the fact that the head wasn't fully 'hemisphered' but was only relieved around the inlet valve.
It's not that I don't believe you Ray- it's just that I don't have enough money to try things that might or might not work... If these pistons made all the difference why didn't they run them in the cars standard?

I know you won't believe me, but it's true. You don't need new pistons and liners, you just need those pistons... or pistons made just like them.
I have just managed to locate some pistons on e-bay for $130 US- so that has made the decision for me, however this unique piston design is definitely something I am going to bear in mind when building a full race motor- do you think that piston crown shape would be of benefit in a turbocharged motor? (I am building a fuego turbo motor at present too...)

The A6 is a Cosworth grind... a mid-sixties full race grind as used in things like F2 etc.
So that grind would have had a lot of lift then?- according to Alans post about lift and HP estimates you would have been revving to around 8000rpm?! Whoever put that motor together must have know what they were doing- I need something that will definitely hold together for a few years.

And yes, it would have to have been close to 200bhp at the flywheel, and it never gave any trouble whatsoever.
Click to expand...
Maybe tuning gear was cheaper in those days? ANother thing of course is that the dyno's can vary considerably in their power estimations- wsa yours run on a dyno Ray?

Cheers Ben
 
Ahem, apologies if that last post was hard to understand/read.... deal

I forgot to add that engine builder advised a slight bump in compression - no more than 9.6:1 on pump gas was his recommendation...so no doubt the head will get planed after checking it and whilst it is undergoing new valve seats/guides etc

Also extractors at a later date- around $500 nz to get some made up- freeflow exhaust on it already (2 1/4") should be sufficient.

Ben
 
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