Engine Talk

[Markie]

Hey all,

 

Still trying to learn things. But I have a few questions.

 

For replacing con rod and their bolts, do you have to have the engine out, as it looks like the bolts do up from the crank side and therefore I am guessing are impossible to do if you dont have the engine upside down?

 

Also, for running 600+ would it be safe to say that all I would need to replace really are the con rods themselfs and their bolts?

 

All other internal stuff should be ok?

 

Thanks in advance,

 

Marcus.

[bignum]

Havent touched my engine yet but this job defo sounds like engine out, i think just getting the sump off with the engine in situ is a royal pita, good luck.

[Thorin]

Just the rod bolts would be advisable AFAIK.

[Lucifer]

Hey all,

 

Still trying to learn things. But I have a few questions.

 

For replacing con rod and their bolts, do you have to have the engine out, as it looks like the bolts do up from the crank side and therefore I am guessing are impossible to do if you dont have the engine upside down?

 

 

 

Possible but a right PITA due to the subframe being in the way.

 

 

Hey all,

 

Also, for running 600+ would it be safe to say that all I would need to replace really are the con rods themselfs and their bolts?

 

All other internal stuff should be ok?

 

Marcus.

 

Absolutly not. For a genuine 600+ then you will need to change alot of internals. People who say 600 is acheivable on teh stock internals are not lying at all, but it wont last 2 seconds if you actually want to drive the car.

 

If on the other hand you wna tto brag down the pub, and put your foot down once a month then im sure it woudl be fine.

 

If you want a 600 BHP usable and reliable car, build a 1000Bhp Engine and the drive train to match.

[Thorin]

If you want a 600 BHP usable and reliable car, build a 1000Bhp Engine and the drive train to match.

 

Of course, if money wasn't a problem... Ian C seems to be managing ok though.

[Lucifer]

Of course, if money wasn't a problem... Ian C seems to be managing ok though.

 

Like I said it depends on how you want to drive it.

 

Extreme 1

----------

 

Drive it to the shops and back on a Saturday after noon, never above 5000 RPM

 

Approx reliability - 10 years 100,000 miles on a new engine

 

 

 

 

Extreme 2

----------

 

20 Laps of Donnington Park every day rain or shine

 

Approx reliability - 1 month 1593.4 miles on a new engine

 

 

Its all relative - also what hasn't been taken into account is the current life left in the engine. You are correct about the money thing, but there is no such thing as a cheap reliable 600 BHp "Driven" car.

[Markie]

So to have 600+ its going to cost a shed load more than just the turbo/map and fuel upgrades then?

 

What did you mean about drivetrain also, surely thats not needed aswell?

 

Starting to think that keeping it as it is would be a lot better

[Lucifer]

So to have 600+ its going to cost a shed load more than just the turbo/map and fuel upgrades then?

 

What did you mean about drivetrain also, surely thats not needed aswell?

 

Starting to think that keeping it as it is would be a lot better

 

 

Drive train , ie Clutch, wheel bearings, gear box, Diff. Clutch woudl need to be changed for a Very meaty unit depending on Torque output.

 

Ive always said that 500 is a better figure for the road and you can run that hard with somedegree of reliability.

 

Forget pub figures / talk, a Genuine 500BHP (DIN) is a HUGE amount of power that the majority of people on this board would never use all the time anyway.

 

My street car will produce a genuine 525 SAE DIN and it will be faster point to point than most 700 bhp Supras. Dont forget you need to get those ponies to the floor!

[Markie]

Drive train , ie Clutch, wheel bearings, gear box, Diff. Clutch woudl need to be changed for a Very meaty unit depending on Torque output.

 

Ive always said that 500 is a better figure for the road and you can run that hard with somedegree of reliability.

 

Forget pub figures / talk, a Genuine 500BHP (DIN) is a HUGE amount of power that the majority of people on this board would never use all the time anyway.

 

My street car will produce a genuine 525 SAE DIN and it will be faster point to point than most 700 bhp Supras. Dont forget you need to get those ponies to the floor!

 

Any thoughts on what internals needed for that power then?

 

Read a bit on Terry S's site and he upgraded the rods and bolts.

[Ian C]

Of course, if money wasn't a problem... Ian C seems to be managing ok though.

 

Why thank you. I can't recall ever talking about my power figures down the pub though

 

Cracking the rev limiter with the Ultimate also took more than a few pulls past 5000rpm at 1.4bar Still haven't shat a conrod out the block in 20k miles. I'm not the maddest driver in the world but I do enjoy leaving roundabouts as dots in my rear view mirror on pretty much every drive.

 

These engines are marvellous. I've seen a 600bhp one with the head off and there were still honing marks in the cylinders. B'Have had a similar experience, 5 years of a T61 and it was in perfect nick internally. I've heard of engines letting go due to det, and overrevving, but not many (er, read none) fatiguing a rod.

 

Having spoken to Terry and Digsy, I've sided with Digsy and am leaving the stock conrod bolts in (Terry and I agree to disagree on this point ). He says that you could make the bolts out of whatever you want, from cheese to unobtanium, as long as they provide stock clamping force by being done up as tight as stock, they offer the same strength as stock. Of course, a stronger rod bolt can be *done up tighter* which makes it "better" but also ovalises the conrod bore and can cause more problems than it solves.

 

Having a cared for engine with regular oil changes, and good supporting stuff to keep the fuelling and cooling correct, is what keeps these things alive. I doubt it'd last the LeMans24 but who drives like that? I wouldn't go past 600ish brake as it's reaching the limits of drivability on the road anyway. 2 years on and I'm still saying "it's enough power"

 

-Ian

[Alex]

Like I said it depends on how you want to drive it.

 

Bah Ian posted just before me

[Markie]

Ian, what power/turbo you running and did you upgrade any internals?

[Ian C]

A Boostlogic T67DBB. Bone stock engine barring cams. Dyno'd at 580 at the wheels, 631 at the engine at 1.4bar on Optimax.

 

I usually run 0.9bar in the wet and 1.2bar in the dry though.

 

-Ian

[Markie]

That kind of shows the right cooling and A/F ratio across the revs the stock will hold up okay then.

 

Guessing the T67 is the biggest you want to go then on stock and not too much pressure either.

 

Much faster than BPU?

[RobSheffield]

Ian, slightly offtopic, but what cams did you go for, in and ex, and would you be sticking with or doing slightly different if you were to do it again?

[paul mac]

Having a cared for engine with regular oil changes, and good supporting stuff to keep the fuelling and cooling correct, is what keeps these things alive. I doubt it'd last the LeMans24 but who drives like that? I wouldn't go past 600ish brake as it's reaching the limits of drivability on the road anyway. 2 years on and I'm still saying "it's enough power"

 

-Ian

 

very well said Ian, i think its easy to look at the "nuts and bolts" side of it but what you say plus sympathetic driving i.e cruising the car after a blast until the temp gauges have come down (30 seconds on a turbo timer is a total waste of time) add a lot to how long the engine will last

[Miguel]

g

 

Having spoken to Terry and Digsy, I've sided with Digsy and am leaving the stock conrod bolts in (Terry and I agree to disagree on this point ). He says that you could make the bolts out of whatever you want, from cheese to unobtanium, as long as they provide stock clamping force by being done up as tight as stock, they offer the same strength as stock. Of course, a stronger rod bolt can be *done up tighter* which makes it "better" but also ovalises the conrod bore and can cause more problems than it solves.

 

 

 

-Ian

 

 

Clampling force aside .What about stretch forces Ie different material will break at different stretch loads no matter what the clamping forces. Just one to throw in the mix

[Markie]

Migster boy, how are you?

 

What are you on about this streching stuff?

[Soonto_HAS_soop]

What are you on about this streching stuff?

 

Different materials can take different levels of force before they start to stretch, once they start to stretch they tend to try and shear.

 

Rod end bolts tend to be "Stretch" bolts when they are inserted, so are stretched when inserted.

 

I used to test this sort of thing at uni, can't remember what results we used to get.

[Digsy]

Clampling force aside .What about stretch forces Ie different material will break at different stretch loads no matter what the clamping forces. Just one to throw in the mix

 

Just to qualify my comments aboutthe stock rod bolt:

 

What I explained to Ian was that the tensile load on the rod would not increase uness he upped the rev limit. What he does with hie e-Manage Ultimate from there on is up to him The tensile load on the rods at TDC exhaust stroke will increase by the square of the increase in speed.

 

After discussing breifly with Terry and comparing the material properties of the stock and ARP rod bolts, it looked like the stockers would be a 10.9 material and the ARP jobs were roughly 12.9

 

It just so happenes that a 10.9 bolt tightened to yeild gives about the same clamp load as a 12.9 tightened to maxium torque (which is what the ARP ones are). Hence the ARP bolts dont give you anything over stock, unless you do them up tighter and risk bore ovality. The main advantage in the ARP bolts seems to be that you can do them up and undo them until the cows coem home without having to replace them.

 

As long as Mr C stays below the stock rev limit, his tensile rod loads will not increase over stock. Therefore the increased tensile properties of the ARP bolts should never come into play.

[Soonto_HAS_soop]

Very good post Digsy.

[Markie]

Ahh I see. Rods are pritty good stock also then?

 

P.s. Bore ovality - Guessing its bad that then? What would that cause? More wear on the crank shaft?

[Digsy]

Ahh I see. Rods are pritty good stock also then?

 

P.s. Bore ovality - Guessing its bad that then? What would that cause? More wear on the crank shaft?

 

 

I'm talking about the rod bolts. We can infer that the rods themselves are OK because Ian (and others) are running 600+ and no one's rods have gone banana shaped yet. I must say that its unusual for a base engine component to be designed to take nearly 200% of its stock load, but the evidence seems to suggest that. As far as the bolts are concerned, I don't see any reason to change them unless you up the rev limit - and even then you should be looking for more clamp load than stock rather than simply putting stronger bolts in but doing them up less tight.

 

As for bore ovality: The rod big end will have been bored out to a perfect circle with the big end bolted on. If you then do the bolts up tighter you run the risk of turning this bore from round to oval, which means that the bearing clearances will not be even all the way around. Its a minor risk, but a risk nonetheless.

[Kranz]

As for bore ovality: The rod big end will have been bored out to a perfect circle with the big end bolted on. If you then do the bolts up tighter you run the risk of turning this bore from round to oval, which means that the bearing clearances will not be even all the way around. Its a minor risk, but a risk nonetheless.

 

Which is where a properly built "blueprinted" engine would be required where all these variables are measured.

The chosen bolts would be tightened up in the con rods and torqued up to the correct torque, then the internal diameter measured at 6 or more points to check for ovality. Then the bore would be honed with the boilts torqued up if it was outside the spec.

 

High RPM's are the killer for rod bolts, the lower in the RPM range you can make your 600 hp the better for their reliability.

 

The rods themselves are affected by RPM and high combustion forces, especially at very advanced timings. Detonation also can cause the rods to bend, so the higher the power the more damage can be caused by det.

[Ian C]

Much faster than BPU?

 

My god yes Ludicrously fast. The performance data I've got gives me 40 to 60mph in one second (when on boost) in 2nd gear, with RLTC having a hernia. From 65mph to 105mph in 4th, it's 10mph per second.

 

Ian, slightly offtopic, but what cams did you go for, in and ex, and would you be sticking with or doing slightly different if you were to do it again?

 

I had 256in 264ex HKS cams from my hybrids days. They are a huge improvement over stock, give a good kick at around 5500rpm, and let the engine breath well all the way up to the redline of 6800rpm. I'm trying the 272in 264ex combo at the moment but until I've finished testing I'm saying nothing about that setup.

 

Clampling force aside .What about stretch forces Ie different material will break at different stretch loads no matter what the clamping forces. Just one to throw in the mix

 

Once the bolt stretches the conrod will start fretting, so it's irrelevant I guess - your bearing is toast. That's how I see it anyway. Digsy explained it better than I understood it anyway.

 

Just to qualify my comments aboutthe stock rod bolt:

As long as Mr C stays below the stock rev limit, his tensile rod loads will not increase over stock. Therefore the increased tensile properties of the ARP bolts should ever come into play.

 

I assume that should be "never" and not "ever". I found that power dropped off noticeably when beyond the stock redline - considering I'd do better in a taller gear rather than hugely increasing the stress loads as described above, I put the stock rev limit back It was nice to beat the limit from a techie perspective, and some people rather like it revving higher, but I'll stick to stock bolts and the stock limit. From what I understand the more power you get the bigger the compressive loads become, but TDC on the exhaust stroke is what mullers the conrod bolts and that only increases with higher revs... (edit - just realised Digsy said that bit already )

 

-Ian