23 replies to this topic

[928s]

Guys with the Porsche 928 engine I am building, 6.0 litres and a rev limit of 7500 rpm, I was wondering if hi mount injectors will help with power. The engine management system will run both low hi mount, the low mount injectors have been upgraded to multi hole design, also I will increase the fuel pressure, the top mount injectors will be suzuki or kawasaki, multi hole, I think they are 8 to 12 hole, my eyes are going on me, given I'm an old bastard at 42. :

These modern injectors must help, as the factory ones are literally like a hose instead of a spray. The new Suzukis etc make 175 hp per litre so they are doing something right. Given that this mod wont cost much, say $500 at the most, if it will be worth power I want to know about it.I think the biggest problem will be tuning it? Also I would have thought that it will cool the incoming charge, that it self should make power.

Thanks Greg

[Bill Sherwood]

Yes, you should get something like 3% - 4% more torque, if it's all done properly.

[928s]

Thanks Bill, great web site you have BTW.

Greg

[NRoshier]

there is no gurantee that the multihole injectors will any power whatsoever. Their use is often more an emissions control benefit.

[928s]

there is no gurantee that the multihole injectors will any power whatsoever. Their use is often more an emissions control benefit.

Porsche upgraded the fuel pressure from 43 psi to 55 psi on the 928 and other modified 928 engines that been built run better with smaller higher pressure injectors also. Well at least in regards to idle quality.

F1 engines which use very high fuel pressure to basically atomize the fuel almost to a gas level have benfited from this practice and I think we can be sure that they aren't too worried about idle quality. So the smaller nozzles allowing a better (read more complete) and I'm sure cleaner burn and maybe this also leads to better fuel economy too? As far as power goes I would have thought that the hotter the burn in a shorter time without problems associated with detonation will lead to more favourable combustion characteristics as such the ability to produce increased power will be more likely, IMHO.

Greg

[NRoshier]

Greg by all means try it. I have been researching it for an article in Race Magazine and have found no one to support the theory, which I also once subscribed to. The injectors are designed to work well at a specific pressure or pressure range, there is no gurantee that they will atomise better at a higher pressure.

[Bill Sherwood]

Adding to what Neil has said, you (typically) would only want single pintle injectors out in the ends of the trumpets, not multiple pintle.
I'd still only use a twin pintle with the injectors in the head as well.

[928s]

By Bill

Adding to what Neil has said, you (typically) would only want single pintle injectors out in the ends of the trumpets, not multiple pintle.I'd still only use a twin pintle with the injectors in the head as well.

Could you please elaborate on why? The Ford racing injectors are 4 hole so are the new Chevy LS7 injectors, given my engine is quite similar to the LS7, i.e a big 2 valve engine, that revs to 7500, I thought I couldn't be too far from the mark? The current injectors in my 5.0 litre engine look like a syringe squirting, that can't be good, also if the benefit is emissions only I wouldn't probably do the conversion, if it was emissions and fuel economy then I think it is worth it to have multi hole injectors. I have to buy new ones so it is not like I'm throwing some (good injectors) in the bin.

As to where I was going to mount the hi injector, the port is a very straight high velocity port, the manifold is also very straight after a 90 degree bend which comes from the plenum, I can post a pic if need be. I was going to mount the injector right where the bend is, so that the injector is pointing straight down to the valve.

Greg

[Bill Sherwood]

Originally posted by 928s
By Bill

Could you please elaborate on why? The Ford racing injectors are 4 hole so are the new Chevy LS7 injectors, given my engine is quite similar to the LS7, i.e a big 2 valve engine, that revs to 7500, I thought I couldn't be too far from the mark? The current injectors in my 5.0 litre engine look like a syringe squirting, that can't be good, also if the benefit is emissions only I wouldn't probably do the conversion, if it was emissions and fuel economy then I think it is worth it to have multi hole injectors. I have to buy new ones so it is not like I'm throwing some (good injectors) in the bin.

As to where I was going to mount the hi injector, the port is a very straight high velocity port, the manifold is also very straight after a 90 degree bend which comes from the plenum, I can post a pic if need be. I was going to mount the injector right where the bend is, so that the injector is pointing straight down to the valve.

Greg

I agree that a thin stream of fuel isn't very good, and you should look fotr an injector that sprays a much finer mist, in a cone pattern.
And as for the hi-mount injectors, I'm sorry I assumed they'd have a straight path to the valves - So I'm guess that again you'd need a good spraying injector. So if you can mount that injector as far away as possible and yet straight at the valve that will help as well.
But I'd try the multi-pintle injectors if you can first.

The engine I'm putting together now will also have two sets of injectors - One set close to the head in the inlet manifold and the second set out in the ends of the inlet trumpets.

[Hans Derbe]

I think swapping out old injectors with modern ones can't hurt. Whether it is worth to go for shower injectors on your engine is another question. On these little motorcycle engines the top injectors aren't active below 6000 rpm or so. So 7500 rpm are quite low when compared to motorcycle/F1 engines.
M. Illien said in an article when they upped the fuel pressure from 12 bar to 120 bar it resulted in 3% more power due to better fuel atomization, which is quite a lot. But again this is for an "on the edge" F1 engine turning 18000 rpm and I doubt 12 or even 120 bar fuel pressure are practically usefull for such aplications as yours.

Hans

[NRoshier]

Originally posted by 928s
By Bill

Could you please elaborate on why? The Ford racing injectors are 4 hole so are the new Chevy LS7 injectors, given my engine is quite similar to the LS7, i.e a big 2 valve engine, that revs to 7500, I thought I couldn't be too far from the mark? The current injectors in my 5.0 litre engine look like a syringe squirting, that can't be good, also if the benefit is emissions only I wouldn't probably do the conversion, if it was emissions and fuel economy then I think it is worth it to have multi hole injectors. I have to buy new ones so it is not like I'm throwing some (good injectors) in the bin.

As to where I was going to mount the hi injector, the port is a very straight high velocity port, the manifold is also very straight after a 90 degree bend which comes from the plenum, I can post a pic if need be. I was going to mount the injector right where the bend is, so that the injector is pointing straight down to the valve.

Greg

Some engines can be very sensitive to injector performance and placement and how one responds cannot be judged from another engines response...it is an expensive guess if you decide to do what say GM has done.
The poor quality (relative to a fine spray) of your current injectors may be down to their old/poor condition. However do not forget that they will be spraying onto the hot intake valve and this will vapourise the fuel.

[Bill Sherwood]

Originally posted by NRoshier
However do not forget that they will be spraying onto the hot intake valve and this will vapourise the fuel.

That could be an expensive guess as well.

[Powersteer]

Bimota Santamonica

[NRoshier]

Originally posted by Bill Sherwood


That could be an expensive guess as well.

Not really. manufacturers did it for years...e.g. batch fired in the camira. I've been chasing some leads on injector choice for 5 months now. My initial concepts of droplet size/power etc are in tatters!

[928s]

Hi Bill and others, I thought I should let you know what I have been doing with this engine design, that way you have a better grip on this crazy project. Also I will hopefully give some people an insight into the Porsche V8, I hope I don't get again just put a Chevy in it mate. If anybody does know where I can get copper infiltrated valve seats PLEASE let me know, or if anybody knows who makes the LS7 valve seat that would be helpful too. O.K here we go.

Now in totally redesigning the 928 engine I went to where the latest
technology is being used for this style of engine, that was Nascar,
Nascar might seem bit of a joke and personally I can't stand to watch
it but their engine builders are very clever.

So my engine is a 2 valve overhead cam V8 with hydraulic followers
and at the time it had the longest belt of any engine built, maybe
still today? The belt was made by Gates who also make the Jesel belt
used in Nascar, so an early connection there. The engine capacity
started out at 4.5 litres and the was expanded to 4.7 litres,
eventually it made it to 5.4 litres and with 4 valves per cylinder,
it is basically the same block with minor changes.

Anyway my car came with a 4.7 litre engine and 310 flywheel hp. It
was redlined at approx 6200 rpm and had an oiling problem when put on
the track due to a few reasons but many a very shallow sump and a
massive windage problem

My big engine that I'm building is 6.0 litres, it has a billet crank
made by Moldex in Detroit, it has all the latest technology that I
designed into it, such as Honda rod journals, Honda rod journals are
a massive step forward in controlling mass forces and friction, for
my engine they mean an extra 7 to 8 hp at 7000 rpm and a massive
reduction in rotating mass, the journal are 30% lighter than the
standard Porsche or Chevy which use 52mm or 53.34 mm respectivally.
This means that my rods are the same weight as a Titanium Ti rod if
the larger journals were employed.

This doesn't even take into consideration the weight saved in the
crank. The one potential downside is the crank pin overlap, this on
the 928 engine is not a problem as it's main journals are 70 mm. The
pistons I have employed are made by Mahle and are forged 4032, and
then coated with Ferroprint, this is a iron based screen print, the
pistons need this because of the cast in liner is made from a
hypereutectic aluminium.

This is an extremely low friction surface, infact the best in the
world, I was told this by a Porsche engineer, who said that the
Alusil was better than Nicasil. Nicasil is a ceramic type coating
that is applied to the bore surface, even the Nascar guys do this.

I managed to remove 1/2 a kilo of weight from just my rod and piston,
they now weight 1.1 kilos, I'm hoping the bigger stroke crank will
only weigh about 21 to 22 kgs I will know this week over the standard
28 kgs, so there are massive savings here, the crank is also a 8
counter weight crank versus the common 6 counterweight crank, the
former has a better balance.

The rods I have are also interesting, they are made by Lentz, they
use the Carrillo SPS bolt, it has a massive tensile strength of
285,000 psi, versus standard Porsche of 156,000 psi, the material is
called Multiphase and doesn't suffer stress corrosion and never needs
to be changed, one bolt cost about $40 USD. These rods when used in a
shorter stroked Nascar engine will happily rev to 10,000 rpm!

O.K, the topend, I hope I am not boring anybody BTW, I have increased
the intake valve size from 45 mm to 53.34mm this possible because I
have increased the bore size to 103.124 mm from 97 mm. Also this
allows better airflow due to the unshrouding of the intake valve, you
of course need adequate spacing between the valves, that thankfully
was provided by the Porsche engineers, the combustion chamber is a
wedge shape, like a Chevy.

The intake valves are Ti and the exhaust are steel, I am using
beehive springs that reduce mass and has a very light retainer, I
also went down from a 9mm stem to a 7mm stem. This saved lots of
weight, the weight of a standard intake and exhaust was 107 and 108
grams respectivally. The weight of my new valves are 72 and 78 grams,
the exhaust is quite heavy due to the fact it is made from Superalloy
and can take upto 2400F. These intakes require special treatment
which I wont go into here.

The airflow was increased through the heads from approx 211 cfm to
300 cfm @28 inches of water. This theorectically allows over 600 hp.
I think i will get into the high 500s, although the guys using the 4
valve heads do get 700+ or 600 rwhp! At this power level they are
experiencing cracking in the main webs of the block, my power levels
are lower and I have lowered mass forces where they haven't, I don't
expect to have any problems at all.

The cams have been reground, they are chill cast iron not steel, but
I will have the lifters diamond like carbon coated, DLC, this cuts
friction massively, all F1 engines use this, so do Nascar, cuts wear
also, I will run 0.550" on the intake and 0.505" on the exhaust. I
have custom built my exhaust which I am told repetively sounds
totally awesome, they are equal length headers within 1/2 inch and
then dual 3" with a variable pressure bypass valve.

I could go on but this is the level I take thing to, the car I have
has so many mods, it is seriously fast even with its 5.0 litre engine
that not many modern Porsche could beat it, when it gets its big
engine it will be capable of 200 mph and 1/4 mile times in the 11s. I
also handles very well, it has big modern rubber, 245 at the front
and 295 at the rear 18" rims and 355 mm front discs, Leda adjustable
shocks.

Tell me what you think or would like to know, if you have anything to add, things I may have missed or what I should do. The management system will be Motec M800

Cheers Greg

[Bill Sherwood]

Look good, Greg.

[NRoshier]

Greg, there is perhaps little more that we can assist you with. Why not contact Motec in australia and ask them for advice.

[J. Edlund]

Originally posted by Hans Derbe
I think swapping out old injectors with modern ones can't hurt. Whether it is worth to go for shower injectors on your engine is another question. On these little motorcycle engines the top injectors aren't active below 6000 rpm or so. So 7500 rpm are quite low when compared to motorcycle/F1 engines.
M. Illien said in an article when they upped the fuel pressure from 12 bar to 120 bar it resulted in 3% more power due to better fuel atomization, which is quite a lot. But again this is for an "on the edge" F1 engine turning 18000 rpm and I doubt 12 or even 120 bar fuel pressure are practically usefull for such aplications as yours.

Hans

I don't remember what F1 engine designer said this but anyway; with some engines increased fuel pressure can do a lot for the power output, while other engines won't respond that well. Increased fuel injection pressure from a stock type 3 bar fuel pressure to a high pressure system of say 10-20 bar do more than the next step ; from 10-20 bar system to +100 bar.

There are low cost motorsport fuel injectors for pressures of about 10 bar. There are also more expensive high pressure fuel injectors designed for pressures up to about 30 bar, such as the McLaren TSR2.1 high pressure pintle injectors (these cost over $1000 a piece). High pressure injectors are only availible from a few manufacturers, for example Bosch. They require HPI power stages and high pressure fuel pumps. Right now, these components are still very expensive.

Like already mentioned, multi jet injectors are for low emissions, not high power.

Some info from McLaren regarding fuel injectors:
http://www.mclarenel...app_act_inj.asp

[NRoshier]

TAG injectors have been tried locally by some V8 supercar teams, particularly for high mount applications. However they are a short service item as is most of the fuel system and were outlawed. The additional fear was that if there was a fuel leak and fire it would rapidly get out of hand. I wonder if their use in F1 etc is simply so they can get the reuisit amount of fuel into the engine in such a short time window?

[EfiOz]

Originally posted by NRoshier
TAG injectors have been tried locally by some V8 supercar teams, particularly for high mount applications. However they are a short service item as is most of the fuel system and were outlawed. The additional fear was that if there was a fuel leak and fire it would rapidly get out of hand. I wonder if their use in F1 etc is simply so they can get the reuisit amount of fuel into the engine in such a short time window?

Airbox fires in V8 Supercars are a common occurence anyway.

You did hit the nail on the head in regard to the extreme fuel pressure in current F1 engines. It's mostly related to the very short time available in a power cycle. It reduced the duty cycle to such a point that injector phasing became important again.

And you can get Copper/Berylium valve seats from Del West. Alternatively, we've been using a new copper alloy called ToughMet. It's available locally and isn't so nasty to machine.

Well done with the engine!! Sounds like a beast.

[928s]

EfiOz

Airbox fires in V8 Supercars are a common occurence anyway.

You did hit the nail on the head in regard to the extreme fuel pressure in current F1 engines. It's mostly related to the very short time available in a power cycle. It reduced the duty cycle to such a point that injector phasing became important again.

And you can get Copper/Berylium valve seats from Del West. Alternatively, we've been using a new copper alloy called ToughMet. It's available locally and isn't so nasty to machine.

Well done with the engine!! Sounds like a beast.

Many thanks for the compliments, many many thanks for the lead with the valve seat material. Have you any details of this material? Like Rockwell hardness and material composition? Can I use it on both the intake and exhaust seats, the reason I want to do that is because the valve seats will be interlocked. I don't want a different rate of expansion.

Many thanks to the other responders too, that McLaren site is a real eye opener, I would love one of those lightweight alternators. How much do you reckon they cost? Also I have dropped the idea of the Hi Mount injectors after the responses I got from this board, seems like a lot of hard work for very minimal gain, with the potential disaster thrown in.

Greg

[Canuck]

As a machinist in the oil and gas industry, I work with Copper/Berylium and Toughmet all day (unfortunately none of our stock is large enough diameter for intake valve seats). You can find all sorts of info on both materials from the Brush Wellman site. Toughmet is a copper/nickle/tin alloy we use for severe environments in sub-surface work but Brush markets it as a bearing alloy.

[J. Edlund]

Originally posted by NRoshier
TAG injectors have been tried locally by some V8 supercar teams, particularly for high mount applications. However they are a short service item as is most of the fuel system and were outlawed. The additional fear was that if there was a fuel leak and fire it would rapidly get out of hand. I wonder if their use in F1 etc is simply so they can get the reuisit amount of fuel into the engine in such a short time window?

The fuel injectors used in F1 today use much higher fuel pressures than used by the McLaren TSR2.1 injectors. I believe the latest McLaren injectors are developed together with Bosch. My guess is that they are similar to these:
http://www.bosch-mot...ini-HDEV_12.pdf

Originally posted by 928s
EfiOz

Many thanks for the compliments, many many thanks for the lead with the valve seat material. Have you any details of this material? Like Rockwell hardness and material composition? Can I use it on both the intake and exhaust seats, the reason I want to do that is because the valve seats will be interlocked. I don't want a different rate of expansion.

Many thanks to the other responders too, that McLaren site is a real eye opener, I would love one of those lightweight alternators. How much do you reckon they cost? Also I have dropped the idea of the Hi Mount injectors after the responses I got from this board, seems like a lot of hard work for very minimal gain, with the potential disaster thrown in.

Greg

I don't think ToughMet is as hard as the BW Alloy 25 and Alloy 3 (copper beryllium) commonly used as seats. ToughMet is more intended as a bearing metal which could suit for example valve guides.

As for the lightweight alternator, to you mean the permanent magnet alternators? Permanent magnet alternators also requires a voltage regulator, so they can't be used alone.

McLarens ligtweight wound alternators cost from around $2k if I remember correctly.

[shaun979]

I think it is mainly for atomization, and not for fuel mass or because of time issues. You can always go with a larger injector, just that its injection characteristics probably won't be as good. Trying to delivery enough fuel mass by increasing pressure is one of the most inefficient ways to do it since you need a disproportionately large increase in pressure to raise delivered fuel mass.