Should i buy a blower??

[slater]

I'm building a trick x-flow engine for the fiesta using a 1800 diseasal cank (forged!) It should end up about 1800cc with the +90" pistons I'm going to use.

I'm now turning my attention to the induction system, Id rather not turbo as its boring so the choice is between NA throttle bodies or a eaton charger.

I have a freind whos helping me out an he is a agent for omex so the chances are i will use a omex ecu kit.

If i was to go for a blower

M45 or 62?

Is it best to stick the blower straight on the inlet mainfold (this is how ive seen it done with carbd minis) or is it best to put the throttle body (bodies??) after the charger?

What kind of compression do people normaly run with such a set up on pump fuel?

Probably been asked before but i know we have freindly people who are in the know on this forum!

[CR500Dom]

M45 will be plenty

I would run a single throttle body pre charger, decent intercooler or chargecooler, and bypass from coldside of inlet

I am running 10.5:1 C/R and will be about 9psi but with an 85% efficiency chargecooler set up, DET sensing, and Thermocouples in the exhaust primaries to log Port temps

don't go chasing boost, build a decent compression ratio engine and just run 7-9ish psi, that way the charger is operating at its most efficient and you get a lovely torquey engine

You are looking to increase VE not force feed it

Just a quick answer as I don't have a lot of time but
HTH
Dom

[madmog]

When you have some time, could you elaborate on DET sensing? I thought you would need to lower CR down to 7.5:1 for forced induction to avoid detonation? What is happening when detonation is sensed and how often does your (engine management?) system take countermeasures?

Are you adding an octane booster to achieve 10.5:1 plus forced induction successfully?

Many thanks

Ta

[Deleted]

Tell me more about this 1800 diesel crank...

[samyboy]

like in the volvo redblocks then use a penta crank out a boat gain 200cc + extra strength


this sounds interesting, personally id leave it NA on screaming webbers but thats been done enough times so charge it ;D

[Blown_Imp]

10.5 to one is very achieveable with supercharging, especially as doms engine is all aluminium and with some good chage cooling. Ive also got around 10.5:1 compression ratio and going blown, but i can only do it becuase i have very good intercooling and fully programmable ignition and fuel.

There are a number of things that can affect auto and pre ignition, namely the temperature available and sustained during combustion. The pressure waves that are produced in the combustion chamber by the moving flame front can compress the unburnt mixture and cause pre ignition. This takes a fixed amount of time depending on the engine fuel and configuration, and so the higher the RPM the less chance of knock (theoretically). If the equation is needed i can dig it out!

With programmable ignition the timing can be retarded to provide a slower rise I'm cylinder pressure and an overall lower pressure compared to NA ignition timing with a blower. The aim is to get the same peak pressure as NA and make the area under the pressure graph larger, this is easily achieved with supercharging as the burn is slower, and the curve fatter.

The fuel can be used tocool the charge in the cylinder during combustion as the mass of the fuel and so the specific heat capacity is much higher, this is also the reason why methanol is so detonation resistant.

I say go blown, well intercooled with a NA compression ratio, make sure you have the ignition and injection control and youll be laughing, all the way to a new set of tyres!

J

[CR500Dom]

madmog said:

I thought you would need to lower CR down to 7.5:1 for forced induction to avoid detonation?

Tell me why you think that then

Are you adding an octane booster to achieve 10.5:1 plus forced induction successfully?

Nope ;D

Many thanks

Ta [/quote]

[Blown_Imp]

You do sound jolly arrogant sometimes Dom!

Check this car out - 11.2:1 and 27psi of boost un-intercooled and on lower octane american pump fuel!

www.hotrod.com/featuredvehicles/22838_1989_honda_civic_si/

If the ignition isnt adjustable then the static compression ratio has to be change to counter the faster rise in cylinder pressure (due to the denser charge). If the ignition is adjustable then the dynamic compression ratio can be changed, the dynamic compression ratio is the calculated by the point at which the ignition initiates combustion compared to the piston position. If its on its way up then the sooner the ignition is initiated the higher the pressure will be at top dead centre, so retarding the ignition will result in a comparativly lower compression ratio.

Dom is using the detonation sensor to retard the ignition (i would have thought) this will take place at the frequency the ECU is set at, usually in the kHz range.

Any q's don't hesitate to ask, and i will do my best to help

J

[CR500Dom]

blownimp said:

You do sound jolly arrogant sometimes Dom!

J

;D ;D Sorry J, bad day

Just trying to spark a debate.......thats all

I`d like to know why its assumed that to supercharge an engine you need to drop static C/R....

Its the same thing trotted out time and time again, seemingly without any thought or question

Even on Turbos now its no longer the case

13.5:1 C/R and 4.5bar Absolute Manifold pressure ;D ;D

As you say the ecu will allow me to retard Ignition to prevent Det and add fuel if needed on borderline det

The thermocouples logging port temps will back up the Knock sensor and show when we are getting close as well

HTH
Dom

[Blown_Imp]

Does you ECU already have all the parameters for the det sensors? I have heard that they are a little troublesome to tune, and the frequency of the vibrations have to be isolated to make it retard at with detonation, rather than vibrations from you shutting the glovebox too hard!

I am going to try the BMW way of detonation detection as soon as i can, have you heard about the ionised spark method? If not they look at the voltage to initiate the spark at the plug, they found that if detonation had occured then the spark was easier to initiate, this comes from a higher ionised air content in the cylinder. If the voltage before dischage is lower than normal then it retard the next spark, this is almost instantaneous (onle one detonation event need occur rather then a few) and can be done on individual cylinders, both sensing and action.

J

[BenzBoy]

This is all really interesting.
I must say I struggled with static compression ratios and supercharging for a while when I was researching turbocharging for my (temporarily on hold) turbo project.
Controlling detonation is something that really interests me but I haven't looked into it all that thoroughly - really informative posts on this thread. 21990/10

As for the initial question - strap an M45 to that motherfreaker!

[slater]

jonny69 said:

Tell me more about this 1800 diesel crank...

It happens that it pretty much drops straight in the bearings for xr2 crossflow. Stroke is longer and it is much stronger with proper counterweights.

The hard bit is modifying the tails of the crank and making some special adaptors to allow you to fit your timing gears, flywheel and front pullys

Good info you lot but it does sound complex!

[bodieanddoyle]

yo, dom and blownimp. is there a reasonably comprehensive, upto date book on forced aspiration? and not one that needs a degree to read it. I got corky bells book, nice and easy to read, and relatively upto date (mapped fuel inj. etc.) except its american and I suspect behind the times now. I know some basic thoeries and practices, I'd just like to raise my game, as it were

on topic. slater, no you shouldn't buy a blower. or in fact, do any other mods to the fiesta, or I will get insanely jealous ;D ;D

[imreallyslowme]

blownimp said:

You do sound jolly arrogant sometimes Dom!

J

Classic! ...... you should meet him, he's ugly aswell ;D

[CR500Dom]

imreallyslowme said:

blownimp said:

You do sound jolly arrogant sometimes Dom!

J

Classic! ...... you should meet him, he's ugly aswell ;D

All true ;D but at least I`m not an aging "Strawberry Blonde"

[Mr_Bo11ox]

If anyone knows a really good book on turbocharging i'd love to read it. The science of turbo matching is amazingly complicated, at work we have a computer program to do it but there are a (very) few geezers around who can do the sums with a pen and paper. I have never seen a good methodical explanation of how to do it anywhere, either in Corky bells book, on the Garrett website, or in Alan Allards book, or anywhere else. Everywhere covers the compressor matching and I understand that OK but no-one ever touches on the turbine end or how to make sure the turbine can provide enough work to drive your chosen compressor, nor about matching VNT turbines.

[MWF]

I've not seen any recent publications on turbo charging however I believe some very experienced professionals have written some technical articals for Performance Ford lately.

[CR500Dom]

I think the problem comes when you want to get a further understanding of either turbo or supercharging.

Corky bells books are what I would term a good Basic grounding although the supercharger info is not as accurate as it could be, if you want to go beyond that for turbocharging fundamentals you have to start reading up on Turbine theory, most of which is Gas turbine biased as thats where the research has been done.

Likewise for superchargers, you start looking more into fluid dynamics and compressors for other applications to see what developments they are working on, then you have to work out why they are doing it and what the missing bit of info is (There always is info missing trick is to try and spot it which is why you have to look at things from lots of different angles before deciding what the next stage of questions are ;D

Most people are not prepared to go to those lengths to learn that much about a subject, if they cant find it online or in a freely available publication then they give up

Those that have done their research to gain that knowledge are then, unsurprisingly not going to offer it up that easily.

2 people come up asking questions..... one has done the research and got stuck getting to the next level,(which is not that hard in fairness as especially with superchargers for automotive use there are not that many really useful sites out there) and wants to know what direction they should be looking in to expand that knowledge

The other has heard about supercharging and turbocharging and wants to know how to do it and be given a shopping list of parts

Whats your response ;D

If you just hand out the shopping list to person B, do you actually further their knowledge or learning ?

Is it not better to suggest they go away and do some more research, looking at it from the current start point and what they are actually trying to achieve ?

As for Person A, you could point them in a different direction to that which they might immediately have expected, to expand their thinking on the subject

That way when they come back again, they may have been looking at similar material but have a completely fresh and different outlook on it to that which you have arrived at

That then forms the start of an interesting conversation and an increase in areas of potential research for everyone involved, you both gain from it ;D

Sometimes you need to talk to people in different walks of life and different disciplines to move forwards in understanding of a particular problem, this is especially true in the automotive industry which can get very blinkered in what they are doing.

I have spent a lot of years researching Superchargers, because apart from its relevance to the day job, it is something that interests me greatly, I still have more to learn outside of automotive specific applications, which I will continue to do, just as Blownimp and Mr Bo11ox have with Turbos and will no doubt carry on doing .

I am lucky to work with a lot of very very clever people which also helps ...... the difficulty for me is not getting sidetracked onto something else that I want to learn about

[Blown_Imp]

I totally agree Dom, helping someone who is stuck but has been working hard i am happy to do, someone who wants a free meal can go poke them selves in the eye!

Its funny how when i try and find something out i end up writing a whole list of new things in my little book to do some reading on, its a'hold that thought' situation!

I HAVE to get hold of a comprex wave supercharger, they were only ever put onto mazda 626 diesels in europe, and not here! Turbocharger efficiency, boost from idle, no back pressure, capable of mega boost (2-3 bar), no parasitic losses, and very few parts to break (only one moving part). Ferrari tested on on their turbo F1 car, it dropped 2 seconds from a lap of Spa but was not used as their turbo supplier (KKK i think) got stroppy and wouldent let them out of their contract!

J

[bodieanddoyle]

blownimp said:

someone who wants a free meal can go poke them selves in the eye!

poking now! didn't realise that forced induction was a top secret business that no-one else is allowed to know about...