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Discussion Starter #1
Hi all,

After some thoughts, I have a 2012MY with engine that's perfectly capable of decent power, around 1000hp. The gearbox is Dodston 1-6, Forged A&B baskets, 1200ft clutch, circlip set, HD FWD output shaft & gear, HD rear transfer Drop gears and standard (new) OEM 1st selector fork.

I don't launch, never will and tend to bury the throttle at low revs, change gear well before 7k rpm.

I'm after low down power and the engine easily pushed 830lb/ft on the dyno today.

Question is, where's the torque limit on this setup and what else (diffs, I'm guessing) do I need to support higher torque limits?

All advice gratefully received - I'm new to these cars but not to modified cars.
 

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I have a similar set up gearbox but with PPG 1-6 and run 950lb ft of torque. It's not a perfect Science but i think you will be fine box wise.

Billet front diff housing is next on the list for me as even at lower power levels, failure has taken out the block etc..

Saying that though, there are also people running 12-1300bhp with stock items front and rear.
 

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Burying the throttle at low rpm and changing gear at low rpm is quite possibly the worst thing you could do! Your causing a lot of torque due to load placed (more a concern for rods) but also changing well before 7K its falling back into its max torque band and loading the gears as it changes, all our faster 4.25/stock running gear builds we tell them to drive it like its stolen and change at high rpm to stay away from being in the max torque band
 

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To be safe a billet front diff case with billet bearing holder, ive fitted a billet rear cover with a huge trans brace then theres always DSS shafts on the rear.
 

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Discussion Starter #5
I have a similar set up gearbox but with PPG 1-6 and run 950lb ft of torque. It's not a perfect Science but i think you will be fine box wise.

Billet front diff housing is next on the list for me as even at lower power levels, failure has taken out the block etc..

Saying that though, there are also people running 12-1300bhp with stock items front and rear.
I was hoping someone'd say that. I'm not a particularly "revvy" driver and like the power in early. Limiting to 800ft should be OK, ish! :thumbsup:
 

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Discussion Starter #6
To be safe a billet front diff case with billet bearing holder, ive fitted a billet rear cover with a huge trans brace then theres always DSS shafts on the rear.
Billet diffs were next on my list, strangely enough. Regarding rods, Turbo Tuff/ Litchfield built engine. I'm not doubting the engine for one second, just wouldn't mind reinforcing the drivetrain.
 

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At 800lbs it should be a walk in the park for the engine and box as is. I wouldn't go adding reinforcement now tbh. It's likely something will indeed break or need checking at some point, which is when I'd be whipping out the wish list and chucking the extras in.

I agree with John, I think planting it at low revs and changing early is what gives these engines the hardest time.

I have the billet front diff housing and a quaife front diff. Diff makes a nice difference to handling and the billet case helps me sleep at night.

The next step if you are determined enough is to do DSS axles and then also upgrade the 4wd shaft. Then maybe ront driveshafts - but you're running baby power (like me) so probably a waste of time.

And there are sooooo many different ways to waste money on these cars (which is a rather enjoyable experience) that as you seem set mechanically, you could focus on the other places..... (brakesm, suspension, fancy ecu's, bigger turbos, carbon, wheels, the list goes on)
 

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Burying the throttle at low rpm and changing gear at low rpm is quite possibly the worst thing you could do! Your causing a lot of torque due to load placed (more a concern for rods) but also changing well before 7K its falling back into its max torque band and loading the gears as it changes, all our faster 4.25/stock running gear builds we tell them to drive it like its stolen and change at high rpm to stay away from being in the max torque band
As an owner of a 4.25 who had to have a new set of Synchros earlier this year, I’m trying to get my head around your advice here. Yes I did appreciate that a wide open throttle at ‘low’ revs in any gear is a risk to the engine. So accelerating from rest in 1st (and I have never/will never launch mine) is best done with say half throttle, until what: 4K? And only then flat to the red line? And you are then suggesting that, to protect the gearbox, because torque typically tails off near the redline, it’s Ok to flat shift, but only when close to 7k?
So I am already in the habit, when driving the car when cold, to slightly lift between gear changes to reduce the load on the (cold) gear set. But as soon as I hit 70C transmission oil temp (and engine oil temp, by the way), I then start to drive it hard. But If I understand you correctly, you are suggesting that it is wrong to flat shift with a fully warmed car at anything less that 7K. I assume you would agree then that a slight lift to reduce boost and therefore torque, is a wise thing to do, if we want to change up at say 4K in every gear? If I’m understanding you correctly I find this fascinating, and I will start doing this straight away. I rarely use mine in Auto, but should our driving style change too, for example only drive Auto in Race mode to force upshifts towards a higher rev/lower torque range?
Thanks for your insight.
Richard
 

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As an owner of a 4.25 who had to have a new set of Synchros earlier this year, I’m trying to get my head around your advice here. Yes I did appreciate that a wide open throttle at ‘low’ revs in any gear is a risk to the engine. So accelerating from rest in 1st (and I have never/will never launch mine) is best done with say half throttle, until what: 4K? And only then flat to the red line? And you are then suggesting that, to protect the gearbox, because torque typically tails off near the redline, it’s Ok to flat shift, but only when close to 7k?
So I am already in the habit, when driving the car when cold, to slightly lift between gear changes to reduce the load on the (cold) gear set. But as soon as I hit 70C transmission oil temp (and engine oil temp, by the way), I then start to drive it hard. But If I understand you correctly, you are suggesting that it is wrong to flat shift with a fully warmed car at anything less that 7K. I assume you would agree then that a slight lift to reduce boost and therefore torque, is a wise thing to do, if we want to change up at say 4K in every gear? If I’m understanding you correctly I find this fascinating, and I will start doing this straight away. I rarely use mine in Auto, but should our driving style change too, for example only drive Auto in Race mode to force upshifts towards a higher rev/lower torque range?
Thanks for your insight.
Richard
The low rpm acceleration is more a cylinder pressure problem but also if you think about it with say a Stage 4.5/5 car of which a lot have stock trans shifting at lower rpm and flooring it puts the car right in its max torque band, now thats fine for motor but all the torque is now hitting the gear whereas if you change at redline it drops revs but not right back into max torque band. theres no need to try and balance on the throttle just ask your mapper to pull torque on the gearshift, this is what Dimitri does to try and stop a massive load hit all in one go.

If you watch a car change gear at redline the revs dont go below 6K , not much torque there. Billm Hardys stock 4.25 thats running 5.5 100-200 kmh so is plenty powerful and has a lot of torque is either being driven like a traffic cop is behind it or redlined, its been done a year and currently does 150-200 miles a day every day and has 100's and 100's of dragy pulls on it.
 

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Discussion Starter #12
Interesting chat, this. I'm more used to larger V8's and V10's with my daily drivers, so I tend to drive lazy. In my Audi (750hp RS6) it's pretty much "put in auto" and "floor"; the gearbox kickdown does all the work and in owning 6 of those cars, I've only broken the propshaft on one vehicle, which had a crazy / unknown map - the rest have been fine. I guess the Japanese stuff needs a little more mechanical sympathy.
 

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Discussion Starter #13
Update - Had a few issues and decided to take the car to a local specialist (Gloucester way).

Car is having the injectors changed because it's just running too rich, I also told them to have a good look over and tell me if anything at all is wrong / needs doing.

So I had a call today with the garage and I've got an oil leak coming from the engine casing after doing less than 400 miles. They can't get the downpipes off to remove the Linney Ti exhaust because the studs are concealed from the angle the Turbos have been clocked to, plus the wastegate actuators are really close to the chassis and there's not the tiniest bit of room to work around them.

Coupled with front Brake discs which don't have the correct spacers and have cracks and a lip on them, those need to be changed and also the (OEM, not uprated) brake lines are wrapped around the KW shocks (bad).

Due to the leak, the engine's got to come out. I really hope the people who sold it haven't been inside the engine tinkering as it was sold to me with reciepts for a fully forged, rod job etc. build by a reputable specilaist, less than 1000 miles ago. Just to be sure everything is above board, I've had them drop the sump off the transmission and confirmed I have a Dodston 1-6 set fitted.

Assuming everything is alright with the engine when inspected, we're going to get a Quaife LSD fitted whilst the engine is out and probably a billet rear casing too.

Apparently then we're probably OK with the 830lb/ft it pushed at 1012hp on the Dyno, transmission wise.

I will post an update once the engine's out and we'll see if there's anything else wrong.
 

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So your injectors are? Leaking? Too big or what? Because they can be turned down in the map, The exhaust comes undone from the bottom of the downpipe no need to remove from the turbo if the engines being dropped, I take it the leak is from the front cover! Fallen foul of that one before, hobsons choice, be sparing and hope it doesnt leak or put loads of sealer on and hope it doesnt block the oil pick up. Do yourself a favour and put a billet front case on but make sure they use a billet bearing holder (PRL do one) as the stock cast one can crack and you will still lose a diff.
 

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Discussion Starter #15
Injectors are 1600cc ASNU's and too big, so to get the car to idle the AFR is a bit too high. Dropping down to 1050cc 14 hole ASNUs. They are also noisy. Don't want to take the chance on the leaking engine cover, gonna get it taken out and cover off, also have a look inside and check what's been done in the engine. I'm looking to go for more power on the car soon but need to be 100% sure the engine is as it was built. Billet front diff casing I'd like, not sure how much they are or where to get one from.
 

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Injectors are 1600cc ASNU's and too big, so to get the car to idle the AFR is a bit too high. Dropping down to 1050cc 14 hole ASNUs. They are also noisy. Don't want to take the chance on the leaking engine cover, gonna get it taken out and cover off, also have a look inside and check what's been done in the engine. I'm looking to go for more power on the car soon but need to be 100% sure the engine is as it was built. Billet front diff casing I'd like, not sure how much they are or where to get one from.
Yeah the 1600 ASNU arent really suitable for primaries on a Ecutek set up, Litchfield do a billet front diff but not sure if they keep the PRL bearing holder but you can google that and have one by next week.
Or Ben Linney does a nice billet front diff, id be doing that way before a billet rear cover if thats what you meant in your post you really dont need that at your power level.
 
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