Boost pressure for built engine

[AVOturboworld]

I'd first find out if you are actually only reaching peak boost at 5000rpm, which sounds quite high.

This is more typical of what we see here on 92 octane.

[ChrisD]

Originally Posted by King Tut

Your first response to me has told me all I need to know. I have no desire to provide you with any further information. Enjoy your new found power, however you choose to find it.

haha sorry for not wanting more power for "the right reasons" in your opinion. Jesus, get over yourself. The funny thing is as soon as you asked why I want the extra power I said to my friend I bet whatever I say this guy will not approve... and oh what a surprise, you don't.

[ChrisD]

Originally Posted by AVOturboworld

I'd first find out if you are actually only reaching peak boost at 5000rpm, which sounds quite high.

This is more typical of what we see here on 92 octane.

OK I'll check, but I'm pretty sure from glancing at my boost gauge previously that it is mid/high revs when it hits the highest boost pressure rather than anything like 3K rpm. Oh and I'm using 99 octane most the time.

[Kodename47]

Originally Posted by ChrisD

Oh and I'm using 99 octane most the time.

No, you're using 99 RON It's equivalent to 92.5 octane as most would know on here (that's good 92.5 BTW)

Chris, the basic answer is:
Run lower CR to give you more boost headroom, but at the loss of low end power and raising the spool RPM.

You have to decide whether that is what you want. Some people want a car that has good response, others want a bragging hp/drag car. As pointed out, your boost may be mapped to come in gradually to be kind to the OEM rods. Most would agree it's very expensive (and possibly pointless) to open up the block just to replace the rods and keep the pistons OEM.

[ChrisD]

Originally Posted by Kodename47

No, you're using 99 RON It's equivalent to 92.5 octane as most would know on here (that's good 92.5 BTW)

Chris, the basic answer is:
Run lower CR to give you more boost headroom, but at the loss of low end power and raising the spool RPM.

You have to decide whether that is what you want. Some people want a car that has good response, others want a bragging hp/drag car. As pointed out, your boost may be mapped to come in gradually to be kind to the OEM rods. Most would agree it's very expensive (and possibly pointless) to open up the block just to replace the rods and keep the pistons OEM.

Ah ok thanks for the correction. I did think RON and octane were different but I quickly googled the octane of the fuel I use before posting that previous reply and all that came up was "99 RON" so I thought maybe it is just the same as octane after all.

No I don't want a dyno queen or drag race car, I just want to make mine a bit faster by increasing the boost further (as I know it is not running at 100% of the turbo's capabilities at the moment). I always thought the main thing stopping us using maximum boost from this turbo was the potential damage to the rods and pistons, so I figured getting forged internals would solve that problem and a lot of people seemed to recommend getting lower CR pistons for forced induction so that's why I was going for 10:1.

So, without E85, what options do I have for increasing power? Could I just get the stronger rods, stronger valve springs, and stronger pistons but stick with a fairly high CR (let's say 11:1), and then be able to increase the boost a decent amount? or is there still going to be too much engine knock to be able to increase it much? The main thing I'm trying to find out is whether or not it is actually going to be worth the time/money getting the forged internals installed - if we can't actually up the boost that much afterwards then there's no point really

[frosty288]

Originally Posted by ChrisD

Ah ok thanks for the correction. I did think RON and octane were different but I quickly googled the octane of the fuel I use before posting that previous reply and all that came up was "99 RON" so I thought maybe it is just the same as octane after all.

No I don't want a dyno queen or drag race car, I just want to make mine a bit faster by increasing the boost further (as I know it is not running at 100% of the turbo's capabilities at the moment). I always thought the main thing stopping us using maximum boost from this turbo was the potential damage to the rods and pistons, so I figured getting forged internals would solve that problem and a lot of people seemed to recommend getting lower CR pistons for forced induction so that's why I was going for 10:1.

So, without E85, what options do I have for increasing power? Could I just get the stronger rods, stronger valve springs, and stronger pistons but stick with a fairly high CR (let's say 11:1), and then be able to increase the boost a decent amount? or is there still going to be too much engine knock to be able to increase it much? The main thing I'm trying to find out is whether or not it is actually going to be worth the time/money getting the forged internals installed - if we can't actually up the boost that much afterwards then there's no point really

Water/Methanol injection seems to be what you are looking for, instead of getting forged internals.

[Kodename47]

Piston damage is pretty much solely down to detonation. Rods is torque. You don't need to change anything if you can just increase boost at the top, but I guess you'd need a higher flowing turbo for that?

I'm sorry I can't give you an answer on CR vs boost.

[ChrisD]

Originally Posted by frosty288

Water/Methanol injection seems to be what you are looking for, instead of getting forged internals.

That's not something I'd considered, but I'll do some research on it

[350matt]

with a twin scroll turbo housing you can get something about the size of a GT28 / 30 spooling and making reasonable boost from about 2800rpm - this is on a ported compressor housing and this is a 400Bhp size of turbo

so if you know the size of the turbine and the compressor and what trim is on the wheel you can then make some comparisons to the industry standard turbo machines

I'd say with a lower ratio of 10.5:1 etc you should be able to wake the turbo up a bit earlier with a combination of additional spark and exhaust cam timing
if you research what turbo is fitted to something modern like a Golf R this would give a good indicaiton of what can be achieved with a modern 2.0ltr GDi turbo

[ChrisD]

Originally Posted by 350matt

I'd say with a lower ratio of 10.5:1 etc you should be able to wake the turbo up a bit earlier with a combination of additional spark and exhaust cam timing

But everyone else has just been telling me a lower CR like that will mean the turbo comes on boost later rather than earlier

[350matt]

this is true

ulitimatly how much power do you want? and what sort of torque curve shape do you want?

if the answer is 300Bhp then leave at 12.5:1 with low boost
if its 400 Bhp then you can just achieve this with 12.5:1 ratio and careful tuning
If its 450-500Bhp then you need to drop the ratio and boost it up

it will always be a compromise unless you fancy going the big boost Supercharger route?

[IBill4You]

You might want to take a look at this thread to find a viable metric to set your expectations.
http://www.ft86club.com/forums/showt...highlight=dyno

[IBill4You]

Post #3 from there is about what you should expect to be comfortable with on a stock motor. http://www.ft86club.com/forums/showp...40&postcount=3
GT2871R turbo

#10 E85 http://www.ft86club.com/forums/showp...0&postcount=10
GTX2867 E85

#69 http://www.ft86club.com/forums/showp...5&postcount=69
this shows the curves of 91 vs E85 for the GTX3076R

From these graphs you're not really going to make near peak torque until just under 5k unless you run a smaller turbo at regular compression. Seems like you would probably be fine keeping stock compression and running a big turbo on E85 at 15psi + to get more than you could handle.

[Kodename47]

Originally Posted by IBill4You

Seems like you would probably be fine keeping stock compression and running a big turbo on E85 at 15psi + to get more than you could handle.

E85 isn't an option, we can't get it (or at least not at pumps, in cans it's ~£4 a litre).