Alfa Romeo Forums banner

1 - 20 of 50 Posts

·
Registered
Joined
·
923 Posts
Discussion Starter #1 (Edited)
Hi!

I don't know if this is the right subforum for this message, but anyway, here we are. I'll try to link it from the GTV6 subforum.

Since my 2.5 engine has 275.000 km under his belts, is heavily smoking blue, and some cilinders are under compression... I've decided to rebuilt, but a 3 litre from 75 America (Milano?) was avaliable, so I'll store the 2.5, refresh the 3.0 and install it into the GTV6. The engine have 90.000 km and seems to be well maintained.

I want to build a stock engine with minor tweaks:

- BMW 635 injectors
- BMW 635 AFM
- enlarge intake and exaust diameters (plenum, etc...)
- lightening flywheel a bit

This week, me and a friend started to disassemble the engine. Here some pictures:

Engine block is a bit dirt. Any suggestion to clean it?


Cams looks really good, no scratches.... great!


Some oil-mud deposits here...


Four Golden Lodge HL25, one HL2 and one from Peugeot???


Some questions:

1.- The 3.0 is a bit slow engine compared with the 2.5. Has anyone lightened the flywheel to speed engine rev up? How much and where can I lighten the flywheel?

2.- I'll fit stock runners but I hope to fit 40 or 42mm ones soon. What diameter should enlarge the intakes in the heads? And the exhaust passages?

3.- Any advices, tweaks?

Any info, comments and help is welcome.

Thanks a lot,
Alvaro.
 

·
Registered
Joined
·
2,857 Posts
Hi, Alvaro, We have done some of this a couple of times.. 75 3L in GTV6 and 164 3L on GTV6.
On the 164 we made special runners and expanded the outlets of the plenum. I dont think it helped so very much.. The problem is in the engine inlet, it has to be ported to give any significant power increase.

The bigger AFM meters from BMW has been tried before on track here on 2.5L engine. Alas the unmodified engine was the faster, so I have seen no reason to do this..

About the flywheel you just cannot simply lighten the weight because it has an inbuilt imbalance counterweight to counterbalance imbalance in the crankshaft. So if you just grind away you will get imbalance in the engine. So it is with the 2.5 flywheel: it has different inbalance an you cannot just change over. If you want to do that the whole assembly(belt pulley/crankshaft/flywheel) has to be balanced again. However a company named Performatek has done a some research with flywheels imbalance and they have produced correctly balanced aluflywheels for both 2.5 and 3L. Hope you will avoid pitfalls..
 

·
Registered
Joined
·
923 Posts
Discussion Starter #4
About the flywheel you just cannot simply lighten the weight because it has an inbuilt imbalance counterweight to counterbalance imbalance in the crankshaft.
Hi!

Great advice!! I'll take note.

Do you think a 3.0 is notably slower revving up than the 2.5???

My wish is to build a road engine, a bit faster and powerfull than the 2.5, with a couple of mods oriented to fiability and good running. I use the car four of five times a month to go middle fast on B roads around town.. and for long distance trips.

I'll build a racing 3.0 engine (full of mods) when the Group A GTV6 Rothmans project get in shape.

Best regards and thanks a lot.
Alvaro.
 

·
Registered
Joined
·
2,857 Posts
OK, you are one of the Loubet replica guys. Good luck with the project!

Q: Do you think a 3.0 is notably slower revving up than the 2.5?

No, I think the 3L 12V is a wonderful engine and prefer it over the 2.5 in every respect. In our track car it has revved about 7300 until now without problem and that is a standard 3L with SZ cams!

Performatek alu flywheels:

http://www.performatek.com/Alfa/Drive Line/DriveLinededion.htm
 

·
Registered
Joined
·
6 Posts
I´ve got mounted the 2.5 flywheel on the 3.0 engine, and revs quickly than the stock configuration... The power it´s fantastic and there´s no anormal vibrations from the engine...

If this flywheels, as the stock one, are not balanced as well than the requirements of a motorsport engine, ok, but I dosen´t feel the diference...

Intead, I have mounted the engine from a 75 America, not from a 164. But I unknow any difference into the mechanicals (almost comes fron the electrical procedures, sparks management...).

I´ve also and 164 QV (Quadrifoglio 200 HP), and the engine feels more sightly, softened, than the 75´s one. But the diference comes from the ECU/sensor administratión of fuel, revs and air flow...

I suposse... but with the experience under mi right leg.
 

·
Registered
Joined
·
4,501 Posts
Alvaro,

You're going to have all of the pieces in your hands , so it should be relatively easy to do this right!

You can just take your 3.0 flywheel (or the 2.5 flywheel for that matter) and have it lightened and then balanced along with your crank, the crank-pulley and all 6 piston/rod/ring/wrist-pin/retainer-assemblies! Done. Do not simply bolt over a 2.5 flywheel - the balance factor is not the same and the weight savings is minimal for the risk-reward!

Balancing is cheap and makes for a very happy revving motor! Speaking of revs - I too prefer the power, torque and range of the 3.0 over the 2.5 - no matter what the "sounds" that the 2.5 makes - it's al Alfa any way - they ALL make happy sounds! ;) :D Guys here in the States always talk about the 2.5 that revs-up better over the 3.0, but I have found that this comparison is usually made after driving a long-ratio transaxle 3.0 with the 3.55:1 box, as compared to the 2.5 litre Milanos here that all ran 4.10:1 ratio boxes!

I run a 4.10 in my 3.0 and it revs up just fine! ;)

Any way, I would have the small-end bushings in your stock connecting rods replaced and then machined with an off-set UP of somewhere between .7 to .9 of a mm. Then I would simply have the valve-releases on the tops of the pistons machined deeper by a full 1mm - just to be safe - get them cleaned up and put new rings on. Finally, remove the outer-perimeter edge off of all of the combustion-chambers on the heads and now the compression should be in the 10.3 to 10.5:1-range!

Have the rods shot-peened and polished while they are at it and then everything balanced as mentioned above! You could replace the exhaust rockers with units out of a 164 12 valve motor (a bit beefier I believe than the Milano/75 units) and now you can rev at 7K plus rpm all day long!

As far as cleaning - when the block and heads are completely striped-down, any machine-shop would be able to hot-tank them for you (or soda-blast them) and get it all looking brand-new! New bearings and off you go!
 

·
Registered
Joined
·
4,501 Posts
You could also go for a programmable fuel and ignition management system and dump that stupid AFR completely - that would make this baby breathe fo sure! Some say that the AFM is not that restrictive - I think that it is!

On a stock standard 3.0 12 valve we see an increase of 15 horsepower routinely at the wheels from going programmable and removing the AFM! (Without doing ANY other mods!) Programmable fuel and timing is good, but it is not that good - or is it!?

Some of the gains must come from removing the flapper-crapper AFM! With a motor that has had some additional improvements performed, a programmable system becomes even more effective, because it allows one to optimize the parameters of those improvements with more optimal fuel and timing!

With the 50mm cast intake runners, decent headers, the AFM removed and the GoTech stand-alone system, we saw 175 to 182 horsepower at the wheels during about 10 runs ON TWO DIFFERENT BRANDS OF DYNO ON THE SAME DAY!!!

The motor is a stock standard internals, stock heads, stock valves, stock pistons - never opened before 19 year-old 3.0 12 valve with stock rods and stock rockers. On L-jet it never made over 145 horsepower at the wheels on one of the two dynos mentioned above!
 

·
Registered
Joined
·
3,506 Posts
JJ,

In the spirit of "measure it and see," I'd think it would be not too hard to put the AFM back in the intake line just as a passive element to test how well it functions as a simple flow restriction 8^). You seem to feel that the free-flowing intake you have on the Go-Tech system is not a significant restriction. If this is true and it's also true that the AFM restriction is the largest difference between LJet and Go-Tech, then you'd be making about 145 hp again at the rear wheels. If the Go-Tech management has a significantly better fuel map, then you might make more than 145. If the Go-Tech is not much better by itself, then you'll be making less than 145 because of the longer intake path and additional flow restriction.

Monitoring the LJet AFM output would provide you all the information you need to get the real story. If at constant AFM indicated flow the Go-Tech makes more power (assuming similar RPMs), then you can estimate how much of the improvement is due to the fuel map. If the RPMs are different, then you have to factor in the reduced manifold pressure effects, but that's doable, too. Maybe add a Manifold Pressure sensor, but it's probably not absolutely necessary. This ought to work for getting the final comparison made and answering from measurement (is there any other way, really?) what the LJet AFM flow restriction is doing. Any comparisons between Megasquirt systems being run elsewhere would be interesting, both with and without the AFM, because they would also have tinkered with the fuel map but still have the stock air path with its flow resistance essentially unchanged.

Michael
(in a position neither to do the tests nor pay for dyno time)

addendum: Wow! I'm wildly off-topic. I have experience with the 12V 3.0L V6 in the 164, but plan to get some experience with this engine using 164S 10.0:1 pistons in a 3.0L Milano very soon. Sorry not to have real-world experience for the original poster, but that's the way it is. (Michael)
 

·
Registered
Joined
·
2,857 Posts
A lot of what ifs here. I have heard that the flap in airflowmeter steals 5php. The difference is most noticeable at low rpm where you struggle hold the flap open.

In our case we have two 3L engines, one with L jet and one with Autronic, big inlet runners, no distributor, no AFM. Sorry to say to all dreamers of wonderful technical solutions: The one with standard AFM is almost as fast as the one with a lot of extras! :eek:
 

·
Registered
Joined
·
4,501 Posts
Here we go again. To be clear; I never attributed the gains from 145 horsepower to 175-180 to the GoTech or to the removal of the AFM (or to both for that matter.) I estimated the gains from the GoTech addition and removal of the AFM to be around 15 horsepower and arrived at the final dyno numbers along the path of adding the 50mm custom cast intake runners, modified plenum and South African headers.

Also, let's not bleed all over this guy's thread with the usual bench-racer - my engine-management system versus yours - bull**** please! My suggestions come from a position of a modified engine (something that Alvaro may consider) and the standard L-Jet that is INCAPABLE of providing the correct fueling for it. Period.

I don't need to put the AFM BACK IN to prove a point to myself - I've already taken it OUT and ran before and after numbers! The modification is effective on a stock engine and verified on 2 different brand dynos on the same day! The importance of accurate fueling on modified engines - I won't even begin to entertain a debate on that one!

The current GoTech installation in my street car referenced above does run MAP; I run TPS on the 3.7 race car and the GoTech allows for a blend of the two to be used as well!

Bottom line - I have never seen a stock-internals 3.0 12 valve that makes that kind of power on L-Jet/L-Jet modified and a AFM in-line. It's not the GoTech per se that makes this possible; it is a basic principles of sound fuel and timing management (and less intake restriction I dare say), that makes this possible - no matter what system you install!
 

·
Registered
Joined
·
2,857 Posts
I think our Autronic engine must have around 182 RwHp and the L-jet probably not much less, about 170-174 Rw.Hp. The driveline loss in the GTV6 is 31Hp so then one can calculate engine Hp.

145Hp out of the question in our case, that must have been a dull engine.
 

·
Registered
Joined
·
3,506 Posts
Here we go again. To be clear; I never attributed the gains from 145 horsepower to 175-180 to the GoTech or to the removal of the AFM (or to both for that matter.) I estimated the gains from the GoTech addition and removal of the AFM to be around 15 horsepower and arrived at the final dyno numbers along the path of adding the 50mm custom cast intake runners, modified plenum and South African headers....

I don't need to put the AFM BACK IN to prove a point to myself....
I was suggesting a way to actually measure the effect of the AFM, which _is_ something speculated about many times by many people. (I think JJ may even have done it once in public.) A measured and documented power increase has resulted from a sum of many things. All that I suggested was a way to measure something very like the power reduction from the AFM flow restriction all by itself. No finger pointing. No "mine is bigger than yours." Only suggesting a measurement that looked possible. And telling the poster than I have plans (and plans only, at present) to put 10.0:1 pistons into a 3.0L LJet engine.
 

·
Registered
Joined
·
418 Posts
Here's a couple of threads that might help with flywheels:

http://www.alfabb.com/bb/forums/showthread.php?t=46463

http://www.alfabb.com/bb/forums/showthread.php?t=38390

I would do the flywheel. IMO, more important (and less costly) than gear lightening. Gear lightening I think will only prolong synchros. I did my flywheels like in the pictures from above and it's very driveable. Only hops and lurches when I'm indecisive with the accelerator:D If the motors ever out again I'll take more off the front one.
 

·
Registered
Joined
·
923 Posts
Discussion Starter #16
Hi!

More news.
We've just open the heads up.

The cilinder bores are intact, exterior is not corroded, no carbon deposits on piston heads, conbustion chambers clean, minor pitting in exhaust valves.

I thint the engine was rebuilt some time ago and was little used since.
This week we will check the bottom end and valve guides.







Boys, thanks a lot to all, your comments, advices were very usefull.
I decided I'm going to do some minor updates and adjustments to the engine, only.

- Bigger injectors and AFM
- Some porting work
- Matching weight conrods and pistons
- Polishing conrods

Rest of the engine will be stock.
The actual 2.5 engine is a bit tired, with two pistons under minimun compression, great oil consuption... so I think this engine is producing no more than 130/140 bhp to the flywheel... with the 3.0 I hope to get an increment of 50 o more bhp, so I think it's a pretty number... it will pull like a beast, and enought to get my driving license supended for loooooooooooooong time.

More pics and news soon, stay tuned!

Best regards, folks!
Alvaro.
 

·
Registered
Joined
·
324 Posts
would have to agree with JJ here. And this is how I see it as 2.5 and 3.0 12 valve go.

Consistency is required in testing. Its no good saying "well I removed AFM on my 2.5 and fitted CSC headers, it made no difference!" then concluding that it therefore will make no difference to the 3.0 either. A little bit of alfa history knowledge is required to understand why the 3.0 can readily respond so very well to minor breathing tweaks, where the 2.5 behaves more reluctantly.

The factory 3.0 units were more powerful than the 2.5 granted, however, the full potential was not tapped. Alfa were trying to be efficient at the time and I believe they used the 2.5 plenum, intake runners, and exhaust manifolds for the new 3.0 in the 75, since they already had the spares as part of their stock holding. These were fine for the 2.5 units since they were modelled and designed specifically for the 2.5. But they surely do not allow the full potential of the extra 500cc and bigger valves in the 3.0. though?

Alfa were not building a race engine for the road cars. So long as the consumer saw a reasonable increase in power with the 3.0 over the 2.5, they would be happy, so I rekon Alfa new these parts would restrict the 3.0, and therefore help it get by emissions, especially in the USA.

modified Afm, enlarged plenum, enlarged intake runners, and better exhaust manifolds, alone would make an increase in power, as the 3.0 can now take advantage of its larger displacement and bigger valves. Couple these mods to some porting/polishing and removing the afm completely will help even more.

This logically explains why bigger runners, csc exhaust manifolds, and bmw afm, seem to make little difference to the 2.5 on their own, because the 2.5 doesnt really make use of this, it already runs pretty good with all the standard kit installed. You need to enlarge the valves, and install at least S cams, along with these mods, to make the 2.5 respond. i.e make the cylinder heads behave more like the stock 3.0 ones!!
 

·
Registered
Joined
·
923 Posts
Discussion Starter #18
Hi!
Never is too late, so three years later, works restart.

Some previous works done were:
Balancing pistons to exact same weight.
Balancing conrods.
Testing & honning the liners.
Machining 3.0 flywheel to 2.5 weignt
Cleaning, testing and balancing crank, with 3.0 flywheel and 2.5 front counterweight.

Yesterday I started with the reassembly of the main block.

Best regards, Alvaro.
 

·
Registered
Joined
·
923 Posts
Discussion Starter #19
Pictures.

Just one issue:
My documentation noted that the spring of the the oil pump pressure regulator shoul be 54mm long. This spring is 49mm.
 

Attachments

1 - 20 of 50 Posts
Top