AGU engine build for hybrid - The great rod debate!!!?

[VAG-Slag]

I've just got hold of an AGU lump I'm intending forging up... The bores look good, I was just going to get it lightly honed and then build it up with rods shells bearing etc etc.

I've been in touch with a reputable and trusted engineering company, who I know through the trade (and a good friend works for them), to enquire about getting the block cleaned up honed and decked... While speaking with the director the the subject of rods come up.

I tell him what rods I'm indenting on using and the power figures I'm hoping to achieve (300+), "why are you using forged rods?" he asks "the AGU rods are good for 450"... At this point I'm telling him stories of rods bending below 300 and any other pro rod argument I can throw at him.

Our conversation was brief as it was the end of the day and we're both trying to shut up shop. But I know he's built and mapped loads of 4/500+ bhp 20v's with minimal dramas and they're a ****** good bunch of engineers! From what I could gather his main point was that a properly built and balanced 20v with AGU rods will take what ever my hybrid can throw at it, and if there's failure at that sort of power then it's because something is going on.

I did a bit of research and pretty quickly found an interesting thread which raised some good points and pretty much backs up what he was saying in out brief conversation:
http://www.pistonheads.com/gassing/topic.asp?t=1050619

I know this will create controversy and 99.999% of you will be screaming stories at me of bent rods at low powers with little to no investigation into the actual cause! But I'm going to see him in December to discuss this (and the future of this engine) further and would be good if I could have a slightly more informed opinion other than, "these fella's rods bent at 300 brake"

Discuss away!

 

[Prawn]

I'd trust the masses over one place.

What they're saying is, EVERYONE is building them wrong? It's not DIY built engines that are failing on stock rods is it? It's factory engines. Are they defective from new? I doubt it given they'll cover 200k+.

As much as I'm sure you trust this place, I'll confidently say they're simply wrong.

For a road going car; with a small turbo that's going to make it's power reasonably low down in the rev range by way of good midrange torque, the stock rods absolutely DO and WILL bend.

 

[Prawn]

Let's put it another way....
Everyone else says you DO need to change the rods.

What's his big secret? What are we ALL (collective all - tuners nationwide, DIY, racers) doing wrong they seemingly only he knows otherwise on?

 

[VAG-Slag]

I know what your saying lets face it, the insides of an engine after 200k are going to be very different to what they were when they left the factory, even on the most looked after of engines, and possibly this is a reason we're seeing failures...

And at the same time, just because his opinion isn't banded across every forum on the WWW it doesn't make it wrong... I mean, I'm probably going to wack some maxspeeding rods in anyway! But is there any difference between taking a gamble on some non-rifled rods and taking a gamble on this guys trusted opinion? Knowing he has my interests at heart.

I'd also be keen to hear people opinions on the necessity of getting a crank rebalanced after fitting new rods? . .

 

[Gops]

I know how you feel.. but, do you really want to risk it for the sake of £500 rods that's been tested in a 600bhp+ badgerwagen? Or stay with stock rods that have flown out of a standard block at 210bhp. It's not how much power, it's the torque that'll kill them. Look at it like the tfsi's. People running 350+ and no Rod issues but I give it another 5 years and you'll start seeing them. It was the same story with the 8l when mtm were doing BT at 400+ on stock rods. Do that now to a 13 year old car and it won't last simply because the stress put on a 13 year old piece of metal that's been under stress.

I see it as having a Mrs. Starts off strong, but then years down the stress builds up and kills you. Same with rods lol

 

[Adam P]

I had rod failure this year on my s3 and i was running stage 1 with bolt on mods. I now have a new recon engine with the IE rods and balanced crank. I learnt the hard way. As Gops has said, for the cost of them its a no brainer to do them. Think the motto is, 'Better safe than sorry" Especially when everyone who deals with the cars day in day out advises it.

 

[daz-20vt]

if this guy is saying its a fitting or balancing error that causes rods to go
yet he is talking about oem rods
then is he not suggesting that its Audi getting the fit wrong?
tuners dont change oem rods for oem rods???
back in the day no one fitted rods upto 350bhp which was "safe"
hell my mate had an ihi conversion running 330bhp
used to occasionally overboost over 2 bar and he used to kill it everywhere!!!
and yet there are guys running stage 1 now bending rods!?
must just be so many variables to this subject

if i was going to go for 350 bhp now with no rods it wouldnt be with a hybrid
something that builds power more gradually.
though im running rods at stage 1 so i wouldnt actually do that either

 

[antwan64og]

As explained above its torque low in the rpm and fatique that kills rods not bhp.
Big turbos dont produce a big torque spike low in the rpm rang for a start.

Its been shown time and time again that non drilled rods do show increased wear over time. Race motors that live at high rpm suffer less as the oil squirters are doing there thing then.
You could modify you oil system and squirters to help counter this but thats more expensive than just using drop in rods.

People tend to run kkk turbos and hybrids at stupid psi aswell, creates a big torque spike, blows hot air and creates high egts.

 

[VAG-Slag]

Urrggggggggg I knew this'd happen... What have I started!? lol #canofoworms

I was kindo hoping that someone might have something new to ad to the argument other than the ol' "it's torque that kills rods" and "13 tear old rods" etc... But perhaps that's the point, there is no real argument against rods these days.

And gops, I most certainly do not have 500 quid to blow on rods!!! I think I'm just gonna stick with the original plan, spend 200 quid on some maxspeeding rods, get matey to hone and clean the block and I'll do the rest my self. My car's a weekend car anyway and spends most of it's time (when warm) bouncing off the limiter anyway, so I'm not too concerned about lubrication.

Still though, does anyone have much to ad with regards to rebalancing the crank after fitting rods? . . I know the maxspeeding rods are all balanced to within +-1g per set but they'll obviously be a different weight from what was there previously. As I said I'm on a proper budget here, trying to find the balance between not spending money where I don't have to and perhaps spending some money where it might save me some in the future...

 

[<tuffty/>]

My IE rods needed to have a little removed from them when I had my bottom end balanced and they are supposed to be balanced to meh grammes etc... I suspect this is more an overall weight than end to end like most engine balancers will do...

<tuffty/>

 

[antwan64og]

Most of the so called balancing is sh!t to be fair.

We all know that most of the rods out there are made in the same factory, the difference is in the Quality control of the retail companies. Eagle and Scat etc tend to do a good job actually balancing, checking for roundness and maching the rods after production so they can be used.

A cheapo reseller will just chuck the rods on a weighing scale and bag them up together with same weights.
Maybe you'll get lucky and they were all manufactured perfectly and not require further maching.....

Getting the whole bottom end balanced is the best way but from what I've seen the stock cranks remain to be good so can be slapped together if everything measures up right.
Balancing tends to have more place in a high rpm racing motor, at high rpm crank harmonics come into play.
Stockish turbos are too small to support power at high rpm so its a mute point and valve train needs upgrading before then anyway.

At some point i plan to build an A4 TQS on a budget.
Scat rods with a cheapo big T3 turbo, i'll get the honing bit attachment for a drill for £20 off ebay and hone it myself....
But i wont expect it to last forever, anything over 30 hrs would be nice, lol

 

[badger5]

Discuss away!

Discuss what
The evidence is clear

Dont fit rods when chasing bigger power RISK them bending/breaking

/End

 

[badger5]

I know what your saying lets face it, the insides of an engine after 200k are going to be very different to what they were when they left the factory, even on the most looked after of engines, and possibly this is a reason we're seeing failures...

And at the same time, just because his opinion isn't banded across every forum on the WWW it doesn't make it wrong... I mean, I'm probably going to wack some maxspeeding rods in anyway! But is there any difference between taking a gamble on some non-rifled rods and taking a gamble on this guys trusted opinion? Knowing he has my interests at heart.

I'd also be keen to hear people opinions on the necessity of getting a crank rebalanced after fitting new rods? . .

Bad advise from this so called engine builder not to build rods into the thing. They're not big buck items relative to the carnage and destruction not fitting them.
450bhp my **** "safe" on stock rods. No mention of torque I notice

The rifle drilled (properly done!) vs non is not a strength issue but a wear rate issue on small ends. Pretty much any NEW "forged" rod will be stronger than oe used one (100k miles or more)

your engine. build it however you want. your risk

 

[kwistof]

I was kindo hoping that someone might have something new to ad to the argument other than the ol' "it's torque that kills rods" and "13 tear old rods" etc... But perhaps that's the point, there is no real argument against rods these days.

I'm pretty sure I recall reading just the other week that the same part number is used for the rods in the AGU/BAM/AMK etc as was used back in 1990 for the Golf gti mk2 which was churning out a massive 120 odd bhp.

 

[antwan64og]

Look at the two below dynos a T3 turbo with 305hp and a Ko3s with 230hp.
Both have 260+ ftlbs of torque.

Look at the power delivery...... the mental torque spike of the little ko3s is more like to shred gear box syncros (ask @Prawn) and bend rods if you are on track and off and on the throttle.
A ko4 just exaggerates this


T3/T4 s trim stage 3 wheel .63hot .48cold 1.8t Jetta

264ftlbs of torque at like 5500rpm

-KO3s
-GIAC X+ race file on 100 octane
-3" Turbo Back Exhaust

270ftlbs of torque from 3200-4000rpm (little turbo torque spikes)

 

[Prawn]

I think with a topic like this Lewis, the onus is more on you (him) to give evidence that goes against the grain.

What is it that he knows that proves the entire vag tuning scene to be wrong?

 

[daz-20vt]

if he is honestly suggesting 450bhp is ok
so your mere 300bhp will not be a problem in the slightest with him building it!! what are you worried about.
forget them!!
im sure he will fix any rod bend/brake damage free of charge if the worst happens

 

[<tuffty/>]

Facts are...

Rods can and DO fail...

Rifle drilled rods provide better lubrication to the small ends than non drilled rods providing they are not compromised like some are with extra holes and a machined channel in the small end bearing....

There is no magic number for horsepower as its torque and its delivery that kills them....

There is no magic number for torque and its delivery as its hugely subjective...

There is no magic mileage or condition or level of modification that causes failure so its inherently impossible to predict when/if a particular rod in a particular engine will fail...

When rebuilding an engine in any form, fitting rods is a no brainer especially if upping the power

The great rod debate will no doubt crop up again (as it always seems to) the minute another interneterised piece of information appears in some dark corner of the interweb, get circulated and then discussed (again) by the masses..

You can essentially take it or leave it... fitting rods is advisable on 20v's as they are 'known' to fail... heeding this advice is personal choice... like anything in life..

My tuppence

<tuffty/>

 

[daz-20vt]

i say risk it
300bhp isnt that much

 

[Prawn]

Daz - shush. You're not helping

 

[daz-20vt]

wasnt meant to be

 

[daz-20vt]

problem is mr slag
do you want to be cringing everytime you boot it??
you will always wish you haf done it while it was apart
its just not worth it mate
its the best thing ive done to my s3
was always at the back of my mind
i used to drive with not bending a rod in mind
sounds daft but its true
do it
forget it

 

[antwan64og]

Daz - shush. You're not helping

i say risk it
300bhp isnt that much

I-Beam right? Should be strong enough. £160 delivered to your door, what could go wrong,
lol

http://www.aliexpress.com/item/HUR-...4Cyl-engine-I-beam-connecting/1818482185.html

 

[daz-20vt]

id feel safer running oem rods at 450bhp than i would buying something from ali express

 

[superkarl]

id feel safer running oem rods at 450bhp than i would buying something from ali express

Why? they're all made out there
They have their quality control and i bet the sellers hardly check them.
Sellers will want QC reports for them all, if theyre good enough for them, why arent they good enough for you

 

[daz-20vt]

the site man
not the product

 

[Lewis583]

If you are going to be fitting cheap rods, then double check what rod bolts are fitted. There have been a couple engines, on CGTi, (Both used the same cheap rods) smashed to bits (at relatively similar mileage after rebuild) where it appears the rod bolt let go due to the bolts being of poor quality.

If you get cheap rods then at least buy some genuine ARP rod bolts.

Also, that engine builder "specialist" is talking out his ****. 450hp in his dreams

 

[Alex C]

I'm not even stage 1 yet, my rods are going in in December haha

 

[VAG-Slag]

Ok ok, enough of the rod talk already! . . Thanks for your input everybody but I think I knew the answer to my question before hand lol

And as I said, I've not had any sort of in depth conversation with him yet... No doubt he'll probably mention a ridiculously progressive map or something, which is fine with a large turbo capable of producing boost for hi RPM power (and not capable of low end boost spikes) but really isn't going to be making the most of a k300.

Now, if I may, I'd like to change the subject of the conversation to balancing and honing/DIY honing...

I take it that @antwan64og is saying that balancing isn't as important unless your at mental RPMs. I'm still going to be running a standard valve train and rev limit will be set @7.2k, so would it be safe/advisable to skip the balancing procedure in my instance?

Also I was gonna leave honing to the proper boys but having just watched a few rednecks on youtube doing it, it really doesn't look all that difficult. I suppose I'll just have to be careful to maintain the size of the bore and that I don't hone too much away!

The bores look great on this engine anyway, can still see the factory honing marks apart from about a stamp sized spot half way up the bore each side, tis slightly worse on the exhaust side though.
Exhaust side:


Inlet side:


Has anyone got any advise or hot tips to offer when it come to home honing? . . Or should I just leave it to the people who know what they're doing?

Thanks again gents. . . . . And I promise not to ask anything about rods again!

 

[VAG-Slag]

If you get cheap rods then at least buy some genuine ARP rod bolts.

Cheers Lewis... Yea, the maxspeeding rods come with ARP bolts. You really can't grumble for the money:
http://www.maxspeedingrods.co.uk/hi...rged-h-beam-connecting-rods-conrod-x4pcs.html

 

[superkarl]

thatl be from slight piston slap. Most used pistons will show similar marks on the skirts.

honing is easy. You just gotta measure the bores in a million different places to check they are within spec. And make sure ring gaps are also not too slack.

 

[antwan64og]

It depends how far you wanna go and how deep your pockets are.

You can reuse bits if you want or buy new.

like you don't have to get the head/block skimmed when it comes off but its recommended for the best seal, lol.

All the little bits add together to give you the best chance of good reliablity.

Did you get uprated exhaust valve springs? Standard agu ones tend to float at high power, the s3 springs have shims to preload them and aftermarket ones are even better.

 

[VAG-Slag]

honing is easy. You just gotta measure the bores in a million different places to check they are within spec. And make sure ring gaps are also not too slack.

Cheers Karl, will probs give this honing malarkey a whirl my self then... Am aware of ring gaps and measuring the bores but not sure of exact dimensions I should be following. Was gonna message Bill, anyone in the know able to save me/him the bother?

It depends how far you wanna go and how deep your pockets are.

You can reuse bits if you want or buy new.

like you don't have to get the head/block skimmed when it comes off but its recommended for the best seal, lol.

All the little bits add together to give you the best chance of good reliablity.

Did you get uprated exhaust valve springs? Standard agu ones tend to float at high power, the s3 springs have shims to preload them and aftermarket ones are even better.

As has been mentioned Antwan, my pockets are not at all deep in the slightest! . . But I'd still like to be able to put together a reliable enough motor. I'm gonna use new (OE or equivalent) rings and crank shells, the AGU pistons (so long as they're still good), the maxspeedings rods with APR bolts, ACL race bearings, possibly a new oil pump and all the other obvious seals and gaskets etc.

As for the head I wasn't actually planning on using the AGU head, not sure I'd see much advantage with the turbo I'm using. Instead I was going to sell it to help fund everything and I have a spare AUM head here I was going to rebuild with new stem seals (will check the guides for ovality) and lifters.... But that's all still hanging in the balance and very much up for debate! lol

 

[Lewis583]

Regarding the honing of the cylinders. Be wary of the oil squirters , they're only small bits of pipe and it won't take much to potentially bend them.
It would be best to remove them, but if you are careful you could leave them in situ. Just something to be careful of.

Valve springs on an AGU should be ok at K300 power levels I would have thought. It's only when you're pushing the absolute limits of the K04 hotside that they begin to float. It's high exhaust manifold back pressure that causes them to float not necessarily power level.

Block wise I wouldn't bother having it decked unless it is excessively pitted it corroded. Wouldn't have thought it will be distorted but it wouldn't hurt to run a straight edge across it just to be sure.

Head wise. Assess condition of both heads and use whichever is best. An AGU would of course help in regards of flow potential but I wouldn't deem in strictly necessary at this power. Either way I would change all valve stem seals along with a very light skim and pressure test.

Regarding balancing the bottom end, I wouldn't bother, you've stated it won't be revving to the moon so I wouldn't say it necessary.

If no one had got back to you with bore measurement then I will try and have a look at Elsa later.

 

[antwan64og]

Staceys yo yo build thread has most specs and info on page 54 about building the bottom end.

 

[badger5]

Regarding the honing of the cylinders. Be wary of the oil squirters , they're only small bits of pipe and it won't take much to potentially bend them.
It would be best to remove them, but if you are careful you could leave them in situ. Just something to be careful of.

Valve springs on an AGU should be ok at K300 power levels I would have thought. It's only when you're pushing the absolute limits of the K04 hotside that they begin to float. It's high exhaust manifold back pressure that causes them to float not necessarily power level.

Block wise I wouldn't bother having it decked unless it is excessively pitted it corroded. Wouldn't have thought it will be distorted but it wouldn't hurt to run a straight edge across it just to be sure.

Head wise. Assess condition of both heads and use whichever is best. An AGU would of course help in regards of flow potential but I wouldn't deem in strictly necessary at this power. Either way I would change all valve stem seals along with a very light skim and pressure test.

Regarding balancing the bottom end, I wouldn't bother, you've stated it won't be revving to the moon so I wouldn't say it necessary.

If no one had got back to you with bore measurement then I will try and have a look at Elsa later.

Backpressures also high on k03 hybrids... ~2.5:1 pressure ratio exhaust:inlet @ 300bhp levels, 18-20psi plenum pressures - Measured

 

[Lewis583]

Ah didn't realise the K300 used a K03 frame. Christ that's some flow being shoved through it.
Can't help but wonder how high the EGT'S must be?

 

[badger5]

Ah didn't realise the K300 used a K03 frame. Christ that's some flow being shoved through it.
Can't help but wonder how high the EGT'S must be?

depending on how hard you push them... but the 300 number is pegged at that level for a reason

 

[Broken Byzan]

I heard BAM rods were forged. ... hahaha #bamtax

 

[VAG-Slag]

Regarding the honing of the cylinders. Be wary of the oil squirters , they're only small bits of pipe and it won't take much to potentially bend them.
It would be best to remove them, but if you are careful you could leave them in situ. Just something to be careful of.

Valve springs on an AGU should be ok at K300 power levels I would have thought. It's only when you're pushing the absolute limits of the K04 hotside that they begin to float. It's high exhaust manifold back pressure that causes them to float not necessarily power level.

Block wise I wouldn't bother having it decked unless it is excessively pitted it corroded. Wouldn't have thought it will be distorted but it wouldn't hurt to run a straight edge across it just to be sure.

Head wise. Assess condition of both heads and use whichever is best. An AGU would of course help in regards of flow potential but I wouldn't deem in strictly necessary at this power. Either way I would change all valve stem seals along with a very light skim and pressure test.

Regarding balancing the bottom end, I wouldn't bother, you've stated it won't be revving to the moon so I wouldn't say it necessary.

If no one had got back to you with bore measurement then I will try and have a look at Elsa later.

Thanks Lewis, yea I am a mechanic so I'm not a complete nooob... But never built an engine like this from scratch before so just making sure I get the finer details right!

With regards to the bore specs I'm not sure if the info on Elsa will be any good as I know the VAG minimum specs are no good for holding decent boost... As @antwan64og says though, I'll have a look through staceys build thread and see what I can find!

Thanks again guys, can never thank you lot enough for sharing your knowledge! . . Will update my build thread as and when anything happens