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Cinquecento Emma's Turbo Progress Thread!

Introduction

Hey, as some of u may know my turbo cinq is in the middle of having an engine rebuild by my dad. This is the progress so far, and will add to this thread as things happen.

So far......
Port and poilsh and a bit of boring out nearly finished
the only one of these type units I have so much as touched was the Fire unit for a 750MC for Huw Davies, visible at his nice private site, http://racingaspirations.com/index.asp
of course this is a normally aspirated engine, but I did an Uno Turbo a while back for a guy called Nathan Corridon which might interest you, not that much difference betw the two variants all said and done.

We settled for a modest spec, and to keep mapping and cam costs down we put in a prod std Turbo cam. The head was flowed, std valves, yeah, it had forged pistons and was wire ringed, but that's neither here nor there. I figured it would be powerful even with a standard cam as I'd done quite a lot of turbo work on TCs that way. Nathan had a turbo from Turbo Technics designed to produce 18 psi boost, but he never needed it. I built it at 7.2/1 CR. At only 12 psi boost it was quite fast enough and he raced it for a year. I don't know the bhp but I think it was 11 sec 1/4mile or something close to that. Nathan wanted to go very fast, and he said it was enough - if that makes sense..!!

The unit ran with standard ecu and injectors and simply a fuel regulator set up to deliver more fuel, and the car had a wide band Lambda, and was data logged, so Nathan could examine the fuelling in detail. He was a very clever young man and expert with electronics and computers etc (!) who listened carefully to my advices re setting up and the got the thing running like a Swiss watch.
I must confess, we were both surprised how powerful it was at 12 psi, and bear in mind the turbo was probably a bit big.

I tell you this because it demonstates how much power can be gained from a good head job on a turbo unit. Some people used to say it was a waste of time on a turbo head but that's not true. I've never flowed a Fire unit head (hope I got that right Emma), but done right I would imagine airflow gains of 10% plus are possible, or maybe more because you can run much bigger ports on a turbo (or supercharged) unit than a n/a model, and if the head flows well it can be more powerful than an engine with higher boost because it is breathing well and not just pumping up the inlet tract.

Regards!

GC
 
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Excellent post by GC there, which backs up what I have always been told, that head work on a turbo car makes bigger gains than head work on a n/a car, I noticed it as soon as I got my head flowed, even tho i didn't adjust the turbo boost in any way, I instantly registered 0.2bar more boost (now 0.8) on the gauge on standard boost and well over 1bar on initial over boost, I know the bigger TB also helped, thats why I know for me the next stage is a proper (re)profiled cam as the valves are the next choke point now with a bit more lift likely to be needed, then a correct low back pressure exhaust made for it rather than the compromised n/a off the shelf aftermarket exhaust that it currently wears.

I know from having the integrale with its ubiquitous 2L TC engine (something that Mr GC knows a lot about :) ) that head work has released huge amounts of power, even something as simple as a properly designed exhaust manifold and system has shown up clutches past there best when they performed adequately beforehand.

Good to see the thread is back on track, but I liked my posts on it that are now gone ;)

Aaron.
 
Indeed, its why i happily got the work done on mine. Though i may covert to MPI, which'd mean starting again with the 75 head i've got.

Are there any plans to alter the fueling system on Emmas cinq?
 
mase said:
so it seems gettin a ported an polished head even if a turbo is planned makes a lot of sence then :chin:



they arent gone.... just removed from public view ;)
porting or valve de-shrouding is important for flow. but polishing is a big no no. the casting should be left slightly rough so the droplets are broken up. for more info, read david vizard engine book.;)
 
mase said:
so it seems gettin a ported an polished head even if a turbo is planned makes a lot of sence then :chin:



they arent gone.... just removed from public view ;)

The entire inlet should flow well. The turbo application multiplies the flow problem as much more air has to be drawn through the ports. This means the flow limits are rached earlier and therefore any flow restriction removed moves the limits accordingly.
 
Oldschool said:
The entire inlet should flow well. The turbo application multiplies the flow problem as much more air has to be drawn through the ports. This means the flow limits are rached earlier and therefore any flow restriction removed moves the limits accordingly.

so to put it in laymans terms...

increasing the flow rate leads to increases in power?

i guess this is even more important when using a forced induction application like a turbo then?
 
mase said:
so to put it in laymans terms...

increasing the flow rate leads to increases in power?

i guess this is even more important when using a forced induction application like a turbo then?

This is it. Hydrodynamics can be a real beast to tame. At the end of the day porting, induction development, exhaust design and improving the flow of the system is one important part of the tuning (for getting max volumetric efficiency increased puls tuning is an important factor too other than the mechanical tricks), where you try to get as much air into the combustion chamber with the least effort. And hydrodynamics is not a very helpful companion on this and often forces you to weird decisions..
 
Hi Oldschool, you meant aerodynamics, I imagine. Hydrodynamics is fluid dynamics applied to liquids. Ports (well, certainly inlets) follow all the normal of fluid behavioural principles.

The flow problems in inlet ports have an aerodynamic solution, there is only ever one aerodynamically correct solution unfortunately, everything else generates a loss, but finding it is very hard indeed on some heads, especially sidedrafted ones, and can sometimes only be derived by test after test and tiny incremental removal and reshaping.
The difference between gain and loss can be invisible to the human eye even with use of accurate templates.
I worked on Peugeot 205GTI heads during the latter part of last year. One was scratch-prepped, the other a big-name one already prepped that needed a seat replacing and gains if possible. And I had a scrap one to play with so I had the best of all worlds, but they still tied me in knots for weeks. With those heads every single mod has to be tested with valve in, I did over 80 development tests, each test and mod took about 1/2 hr, so you can see how difficult it can be. Slowly the 205 head gave up its secrets, and I not only enhanced my own results but bettered those of the previously prepped head.

I've started trying to get some more detailed info onto my site, wish I had more time. eg: see http://www.guy-croft.com/page16.html

Now - FWIW my exp tells me that:

1. A thin contact face on the valve with a wide contact face on the seat is OK
2. Matched for size valve and seat contact face is good
3. Thin seat and wide valve contact face is bad
4. Super thin contact face and valve seat are bad
5. 35 thou per inch of inlet valve to 60 thou per inch seem to work fine.
6. A valve back-grind from 45 to 30 deg always helps flow.
7. Flow thru the valve throat must equal port flow, if the throat is too small a big port won’t flow and vice-versa
8. Sharp edges in the throat say, with 45 deg seat, 70 deg throat work can better than radiused edges.

(Some of these rules don't apply per se to blown engines BTW)

Moreover - The turn in the section between port and throat (esp. around the short side radius) will always reduce the flow significantly due to turbulence and drag, reverse flow even, so that the apparent flow potential of the port will never be realised in terms of net flow thru the seat (except on very heavily downdrafted engines, eg F1). There is thus a point in port enlargement beyond which increased size will not yield more flow, only a drop in velocity. A 36mm pipe (try it) will flow about 180 cfm at 10", more than any head I know of with 36mm valve throat. A 36mm port will flow the same, but put the two together and the flow loss is huge and all you can do is try to miminise it.

I have yet to find anything that works better than 45 seat and 70 deg throat. I've tried other valve angles ad nauseam, could not better it and mostly the other layouts were worse.

The inner region and valve/seat/throat are very closely interlinked in terms of what works best. Valve shape is a hugely influential factor and you would be well advise to determine the results on a scrap head. Sidedraft heads seem to work best with penny on stick designs and downdrafted heads (valves inclined at 20-25 deg or more to vertical) seem to prefer more of a tulip design, but this should not be taken as a golden rule, as the one thing I do know for sure is that every engine is different and has to be tested to death to get the best results.

There are two reasons why top race engines are now almost all done by
1. Modelling by computational fluid dynamics
2. Flow bench confirmatory testing
3. CNC machining followed by hand finishing
4. Dyno testing and track testing with full data log.

This process gives the nearest to 'perfect' aerodynamic port shape, and repeatability, ie: all heads flow the same.

Regards,

GC

I write on forums for fun only and to proffer a bit of experience. I hope that what I write helps someone somewhere. If this is out of place here, feel free to delete or shift it, thanks.
 
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morning guy.
ive recently seen a new way of doing heads. the heads use a vortex shape to enhance the flow. have you come across this and have any experiance with this?:)
 
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not sure, Andy, tell us more!

BTW Can I suggest u edit and clear my post from your reply? No point in its being published twice (if at all!)

GC


All - I hope I haven't inadvertently hijacked Emma's thread, I'll start a new one if you prefer.
 
Guy Croft said:
not sure, Andy, tell us more!

BTW Can I suggest u edit and clear my post from your reply? No point in its being published twice (if at all!)

GC


All - I hope I haven't inadvertently hijacked Emma's thread, I'll start a new one if you prefer.

if need be the mods can split it.personally i love reading what you guys in the know post up.
find it really interesting to see real world experience laid out
 
now there's the problem. its all hush hush. he will not spill the beans. but his heads are flowing fantastic. yes its that man again, richard beaty. you will need to get hold of a head to disect it. i was just wondering if you had experimented using a vortex principal?:)
 
rned the stuff we throw it in one basket I know us blooming foreigners). But strictly speaking you are right. Still the same principles apply.

By the way, I learn from the posts every day.

I will pm you.
 
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