Here We Go Again Another 16V Dreamer

[Sandy 191]

It looks alot easier than it is. I'd have to write an epic to detail all the issues I came up against with the EW5 I built and that had more suitable port sizes, block height and block design overall. The key issues though, are as follows:

 

You're making a big engine small. It may seem like you get freedom from larger ports and valves "it'll want to rev and rev" etc etc, all the usual thumbnail assumptions; but in reality, compression ratio is a problem with an acceptable piston crown design and the valve throats are simply going to be too big no matter what you do, so gas speed ultimately will be poor and the engine will struggle to show any guts or depth in its delivery. This is true over many over enthused race engine builds, focussed on flow rates and revs. The reailty as I've found it is, that we're not building half an F1 engine and there are optimum compromises in engine capacity relative to the head/block designs for Saloon 4 cylinders.

 

Rods and Pistons, there are alot of cheap ones about these days and mostly they are crap. This isn't obvious on ebay or in a fast road engine build, but if you start to push the envelope and you take engine durability and reliability seriously (and the broader issue of det resistance, oil control and cylinder pressure loss, then this will matter. Great example, Wossner TU5J4 and JP4 pistons, that don't even have the correct valve centres in either case; that's one you can measure and see for yourself, how did they get that wrong? What confidence does that give you in the rest of the more complex engineering involved? Custom rods and pistons are a minefield. I've had to learn how to get them right, to get what I want. 9 times out of ten if you trust a supplier to design them for you, you'll get a misunderstanding on your parts or theirs and what turns up will be wrong; I could give you a list of people of this forum who've fallen foul of this and it's led to misery. Rod quality is another serious issue, don't assume a steel rod is a steel rod and because it has ARP bolts, it must be ok... quality of the design and manufacturing varies hugely and ARP2000s are budget bolts, adequate in most cases, but risky in a serious engine. Witness the "Cat Cam" rods I ordered once from "QEP" as was (off the shelf, took about 6 months), that turned up as "DP" rods, poorly machined and finished, didn't measure as they should, significantly fouled the block and were about 20% heavier than the ones I use now. Mods might suck through there teeth at this, but it's fact, with total provenance and people should know what goes on.

 

Bear in mind also that the XU5 crank is not one I'd be keen to use in a high revving engine. Up to about 8500rpm with light rods and pistons, not likely to be a problem, but buzzing beyond that with the clunking great 158mm odd rods you'll need in an XU5j4, with a decent piston design, running the risk. So are we adding the cost of (and complication/time ordering) a steel crank?

 

I hate to come across as the man with a bucket of cold water, but even overcoming all these issues, which you can with the right suppliers and enough money; the engine is still likely to be one that performs on a knife edge, cam choice with such hugely oversized valves gets harder to produce a decent range of performance, contrary to what's often mused idley about "up the valve size, reduce duration...", the reality I've seen is not like that. I've learnt alot from doing things differently, but also learnt that unless you really know where it's going, you need to be careful how you invest in an engine.

[Batfink 201]

Ok but not all race championships will allow an engine block that has not been in a production 205.

[crossflow 2]

Unless you run a steel crank and spec the engine around the high revs, you might see a very small gain top end with a hugh loss in midrange using a standard crank and rev restricted to 8250rpm.

When doing something one off, expect to pay one off prices to do it right from word go, otherwise it will be just heart ache.

Look at Cosworth BDA 1600cc engine on injection, it willl make 232bhp but does have a rev limit of 9700rpm to give you an idea.

[welshpug 1,661]

180-190 will do me!

 

All perfectly logical from Sandy, sounds like even the xu7 head might be too large on the valves/ports in some aspects, appreciate the oil control comments too, the tu5 in a saxo i service for has pec rods and wossners and i'm not pleased with how much its still breathing.

 

 

You can use a late 8v lump but would need a custom engine mount bracket, the xu7 and the 9j4 dont loom any different to a non pug person though.

 

Maybe a diesel block could be used?...

[Baz 421]

Exactly, Paul's was pretty epic, and still ran an XU5 crank iirc.

[Batfink 201]

Sandy. What manufacturer of pistons should we be using? There's so many out there its a bit of a minefield for people not in your position who has seen many brands through the door.

[309jazzpanda 41]

That's what I got pm'd basically. That's what I like about this forum, when you want advice you know you can message someone or open post and actually get a decent response, glad I started this thread its brought a lot of info to the table for anyone else who was thinking the same as me thanks guys

[Sandy 191]

Sandy. What manufacturer of pistons should we be using? There's so many out there its a bit of a minefield for people not in your position who has seen many brands through the door.

 

Omega and CP are my preferred.

[Batfink 201]

I think you said the EW7 crank is a better option. Can the EW7 crank be used in the XU block?

[welshpug 1,661]

I think it does (XU fits EW) but can;t think why it would be better, it wouldn't make a 1.6 as is!

 

EW7: 1749cc, 82.7mm bore, 81.4mm stroke.

 

XU7: 1761cc, 83mm bore, 81.4mm stroke.

 

XU5: 1580cc, 83mm bore, 73mm stroke.

Edited August 17, 2012 by welshpug

[309jazzpanda 41]

From what I got off Sandy you have to play a bit to get the xu5 crank in, if I read it right that is

[renault 17 1]

I built one of those engines around six years ago. I had to start with a 1.6 litre to get my competition license. It started because I had an mi16 and an xu5 engine lying around, in hindsight they were the cheap bits! A set of omega pistons, 300 degree cams and a few other bits and bobs and I was off! Fair enough you have to rev them to get the best out of them. It was a fairly competitive car but I sold it to go to college and didn't get to do that much with it competitively. The most difficult part of the engine was trying to get the compression high enough, I think in the end I had 11.8:1 , that was with omega pistons (which gave 12:1 on the 1905cc), and the block decked by 1.6mm, the head was machined to give the correct squish clearance. There was minimal valve to piston clearance in it and I just managed to get them dialled in @108 degrees, I would like to have had them tweaked on the dyno but after measuring the clearances during the build I didn't want to stir things around. The car made around 166bhp at the wheels and i think 148ft/lb, Id say if I could have welded up the head to get the compression a little higher there would have been a few more HP to be had. I'm putting a few videos on youtube and I'll link it back here when I'm done.

[renault 17 1]

 

[Sandy 191]

I think you said the EW7 crank is a better option. Can the EW7 crank be used in the XU block?

 

Misunderstanding there possibly, the EW crank is of no use for this. The XU5 crank basically fits the EW blocks, but machining is required to get it to turn!