Precision Billet Turbos

[r32-25t]

I know when I picked up my car from jem I told Adam if it let’s go I’m going to do a 2.8 and he said thats the only thing he would do and don’t change anything else. 
 

I am going to try and get more lift onto the Vcam though 

[meX]

First of all i want to thank you guys for your quick and kind replys. I'm sorry for not introducing myself in advance. As a "inkognito" reading person since a few years, I thought it's my last chance here, to get some serios impressions and feedback from people, which may tried it by themselfs already. Here in the EU, I generally getting in troubles to find the right persons for feedback of first hand experiences. A lot of talkers are also available here and that's making it a bit difficult to find answers..

From my side there is not so much worth to know about. The Skyline was like "oh wow that cars looks awesome" since i was a child. Some years later I was able to fulfill my wishes and at the moment I'm a very proud owner of a R34 GTR Vspec 1999, which is nearly completely stock and of the R32 GTR, which is more or less my "project" car, what i want with more power.

So enough from my personal side, thank you already for the answers and I want to make some remarks and comments to them.

 

On 14/04/2020 at 2:28 AM, Dale FZ1 said:

Welcome to SAU - first time posting!

Firstly - RB26 are not known for strong low-mid range torque.  Your combination of 272 cams and a 6466 that's barely working at 18psi/600hp can't be expected to "wake up" much before 5000rpm. Referring to on-off throttle driving, not what's seen on a dyno sheet.

Secondly - quality of design/fabrication can vary wildly.  Shapes, sizes, angles, merges all play a part in how things work.  Your manifold design, 2 into 1 wastegate pipe merge etc is an unknown.  Was the wastegate pipe divided right up to the valve?  Maybe create a build thread for your car and post up a few pictures to help people see what your car is like.

Thirdly - tuning outcomes can vary wildly.  The engine hardware creates limitations, but so does the tuner's knowledge of how to make something work on the road, as opposed to the dyno.  Something to consider. 

Running 100 octane petrol is no bad thing - your tuner should have capitalised on its knock resistance with an ignition map approaching what might be seen with E85.

Fa set of 4.375 diff gears for your car, the extra rpm in any gear for a given road speed is going to accentuate responsiveness.

Suggestions - install some stock RB26 cams, and spend some dyno time dialling them to what you think you want.  Retain the 6466, talk with your tuner about boost control and what they can do to achieve best spool.  And run another 5psi boost to get an idea of what its capabilities are like.

 

 

On 15/04/2020 at 12:53 AM, ohno1 said:

Some of these responses are inaccurate and misleading.. I feel people are just repeating theories they've read

Once again -- The cams are unlikely to be dialled in correctly

Work from "easy / cheap" to "hard / expensive".. and preferably not go backwards

 

Open inlet 6466 Gen2, 2.6 crank, 272 cams will work together

Might need a couple more pounds boost to get it working more efficiently, but if its coming on @ 5500rpm then there is another issue

 

On 15/04/2020 at 1:15 AM, Dose Pipe Sutututu said:

Super lazy way, just +10 advance the intake cam, will wake up the motor in no time.

*** edit, make sure you use all the available tools to accurate dial in the cam within limits, i.e. could be less than 10 degrees of advance before things kiss.

 

On 16/04/2020 at 1:30 PM, Mick_o said:

Dale is 100% correct its a well proven fact that smaller cams in RB's aid in response. Even going from a stock cam to a type b pon cam will cost you response. Been many track guys that have thrown their poncams in the bin after driving their car, even when the dynosheet looks better it's actually not as good to drive.

My tuner reckons most RB's are over cammed.  (He is no dummy) 272 if you wanna spin it to the moon sure. 272 if you want brapp brapp sic boii idles. But expect it to be soggier in the middle.

I cannot promise you that it's running @ 18 PSI it's also possible that its 17 PSI (i know it's 1,25bars^^) but as Ohno1 already said, does the PSI's matter really that much, that it's coming so late?
I still have my OEM cams in my cellar lying behind the standard turbos^^, does it makes sense to reinstall them again?
At least as Dale mentioned before i want to poste some short pictures of the car to bring you a better overview.

The 6466 sits in front. I got HKS adjustable gears and the 272 degrees cams on the stock bottom end Engine with Metal Head gasket (1,5mm) and ARP bolts. The turbo runs on twinscroll but with only 1 wastegate, the screamer pipe is closed (I wont survive the police here in normal traffic with that) and from the turbo, there is a 4" downpipe to a GESI UHO KAT with 4" and than the 3.5" HKS muffler system.

Please have patience with me, i know it's not looking pretty but at least, it was important that it will run, before it's getting pretty :D.
And as i've seen right now, it's a .84 AR - my bad.

In principle, thats it. If it helps you to provide a dyno sheet than i would send it via PN but I wont make it open here officially for everyone in an absolut public part of a forum.

At least the car is running smooth so far. It's just the f**king laziness, what i did not expected from the setup. Could you find some points according to that which is maybe improveable or is it really just the topic with the "eco boost" variant, which kills my system right now? To go back to twins would be the last choice for me, because than, everything needs to get changed again and secondly, i will get quicker in to the red line of the "power reserve" that i have right now..

In general i was happy with the work, because the car was really not the beauty and it should get better step by step.

If you are now getting me like, try to turn up the boost. Than i have to talk with my mapper. They were not that familiar to boost the stock engine more than it actually is with the ~ 598 NM on the engine.

Best regards meX

PS: If one of the adminstrator wants to make me a seperat topic, than i will go forward to create one :).
 

[KiwiRS4T]

You will notice that no-one is suggesting a return to twins so I hope you have ruled that out.

The two most simple changes you can try are

1. If it is difficult for you to get custom cams put your stock cams back in with adjustable cam gears.

2. Turn up the boost to 2 bar

Then (and this may be the most difficult part) get a good tune. You say your tuner is not familiar with your set up and not comfortable with increased boost. Maybe you need to look around for a tuner who has more experience with turbo engines.

I assume you have an adequate fuel supply. Do you know what kind of pump and injectors you have? 

Also a little worried about your coils - do you know what type they are? 

[Lithium]

Just had a bit of a read through, I have a habit of spending too much time ranting stuff and ending up with people not reading it anyway so to save both of our time I'll try and make some bullet points haha

• Firstly, just clarify - you are saying it is hitting 17/18psi in the mid 5,000rpm range?  Everything I say from here is assuming I've read that right
• First confirmation, a PT6466 should be able to spool MUCH quicker than that on an RB26 if it's allowed some time to load up - like given about the amount of time you'd expect pulling from 2500-3000rpm in 3rd gear or higher.  E85 won't change this much, the effect it has is often more to do with how the engine responds... not the actual boost threshold to a major degree.   How does it spool when you drive it?  Can you describe when it starts building boost and when its "all in" on the road?
• Cams have been mentioned a few times, now long duration cams do naturally have a bias to higher engine speeds, but absolutely not to this kind of degree.  Also, those HKS cams are meant to be drop in and have the same centerline as stock - you don't need adjustable cam gears to run them.   If you do and you have them "dialled" like stock then it should be fine.   They'd need to be installed incorrectly to make the lag this bad, not just "not dialled in optimally".
• Just because it seems like the communication may be murky on this, the suggestions of turning up the boost are NOT going to affect spool, just power.   You won't get it coming on any earlier by doing this.   There could be some gains with boost control setup, but this sounds like it is just lazy as hell when you want it to go.  For what it's worth, what I'm seeing so far makes it sound comparable with a car I've had a lot of time around which runs 280deg cams, a head ported for max power and a T51R SPL running a 1.00a/r open housing.   When targetting 17psi it is making that boost by around those rpm with EVERYTHING much bigger and older school than what you have.
• Have you done much investigation into problems with the car?   To me there is very likely to be something wrong, like cams installed wrong, or a major boost or exhaust leak.   Did you install the valve seat in the wastegate, for example?
• In regards to the tuner, that can definitely make it perform like crap - but the spool is hard to make that bad just with a tune, unless you are saying it feels flat under 5500rpm as opposed to not actually making boost.   Strange call not sharing the dyno plot or any other effort if you are wanting help diagnosing.  Please give any more detail that you can on what you've done to diagnose this, or how it behaves in the real world.
• I would *NOT* change the cams, or the turbo setup to try and resolve this issue.  They would be a lot of work and/or expense when neither should be performing like this - I see too much of this kind of suggestion on this forum when it's clear there is a tuning/mechanical issue which is making a setup which should be able to perform better is not.  There is the chance you might find or inadvertently fix the actual cause for this issue while doing so, but there is no guarantee that you will and you could easily end up with the same issue and have gone sideways or backwards with the setup.    In Oz they're spoilt by being able to use small cams and push heaps of boost in to make good power, but sounds like you are in the same position we are in NZ where you actually need to manage cylinder pressure to make decent power - which is not ideal, but neither is knock

For some reference, here is a dyno plot for a 1.00a/r T4 twin scroll 6466 on an RB26 running Kelford 274/270 cams on E85:

And boost:

 

And a pretty much identical setup but with the cams dialled in for power instead of spool (so "laggy"):

 

 

Edited April 21, 2020 by Lithium

[r32-25t]

Have you tried smoke testing it to make sure there’s no leaks in the pressure system?

[meX]

8 hours ago, KiwiRS4T said:

The two most simple changes you can try are

1. If it is difficult for you to get custom cams put your stock cams back in with adjustable cam gears.

2. Turn up the boost to 2 bar

Then (and this may be the most difficult part) get a good tune. You say your tuner is not familiar with your set up and not comfortable with increased boost. Maybe you need to look around for a tuner who has more experience with turbo engines.

I assume you have an adequate fuel supply. Do you know what kind of pump and injectors you have? 

Also a little worried about your coils - do you know what type they are? 

I will speak to my friend and we will make another slight remap try with the OEM cams. May this helps a little bit and will also talk about that with the tuner again. Some people here are also mentioning that it's a point of optimization of the timing, so I'm going to ask them also.

Sorry for the Missunderstanding. I didn't mean that the tuner is not familiar with high horse power turbo applications. They are if its depending on a stock RB26, because they say, that the engine will probably/mabye break immidiately after tuning it in his stock. That's why they did it on 1.25 bars or 17-18 PSI.

My personal wish was to go for 1.7 Bars (~ 25 PSI) because there are still the stock valve springs in the head and to reach a good power target. But they did not go for because of the stock engine.

There are Injector Dynamics 1000cc injectors installed and R8 coils and also a Nismo Fuel Pump.
 

8 hours ago, Lithium said:

Just had a bit of a read through, I have a habit of spending too much time ranting stuff and ending up with people not reading it anyway so to save both of our time I'll try and make some bullet points haha

• Firstly, just clarify - you are saying it is hitting 17/18psi in the mid 5,000rpm range?  Everything I say from here is assuming I've read that right
• First confirmation, a PT6466 should be able to spool MUCH quicker than that on an RB26 if it's allowed some time to load up - like given about the amount of time you'd expect pulling from 2500-3000rpm in 3rd gear or higher.  E85 won't change this much, the effect it has is often more to do with how the engine responds... not the actual boost threshold to a major degree.   How does it spool when you drive it?  Can you describe when it starts building boost and when its "all in" on the road?
• Cams have been mentioned a few times, now long duration cams do naturally have a bias to higher engine speeds, but absolutely not to this kind of degree.  Also, those HKS cams are meant to be drop in and have the same centerline as stock - you don't need adjustable cam gears to run them.   If you do and you have them "dialled" like stock then it should be fine.   They'd need to be installed incorrectly to make the lag this bad, not just "not dialled in optimally".
• Just because it seems like the communication may be murky on this, the suggestions of turning up the boost are NOT going to affect spool, just power.   You won't get it coming on any earlier by doing this.   There could be some gains with boost control setup, but this sounds like it is just lazy as hell when you want it to go.  For what it's worth, what I'm seeing so far makes it sound comparable with a car I've had a lot of time around which runs 280deg cams, a head ported for max power and a T51R SPL running a 1.00a/r open housing.   When targetting 17psi it is making that boost by around those rpm with EVERYTHING much bigger and older school than what you have.
• Have you done much investigation into problems with the car?   To me there is very likely to be something wrong, like cams installed wrong, or a major boost or exhaust leak.   Did you install the valve seat in the wastegate, for example?
• In regards to the tuner, that can definitely make it perform like crap - but the spool is hard to make that bad just with a tune, unless you are saying it feels flat under 5500rpm as opposed to not actually making boost.   Strange call not sharing the dyno plot or any other effort if you are wanting help diagnosing.  Please give any more detail that you can on what you've done to diagnose this, or how it behaves in the real world.
• I would *NOT* change the cams, or the turbo setup to try and resolve this issue.  They would be a lot of work and/or expense when neither should be performing like this - I see too much of this kind of suggestion on this forum when it's clear there is a tuning/mechanical issue which is making a setup which should be able to perform better is not.  There is the chance you might find or inadvertently fix the actual cause for this issue while doing so, but there is no guarantee that you will and you could easily end up with the same issue and have gone sideways or backwards with the setup.    In Oz they're spoilt by being able to use small cams and push heaps of boost in to make good power, but sounds like you are in the same position we are in NZ where you actually need to manage cylinder pressure to make decent power - which is not ideal, but neither is knock

For some reference, here is a dyno plot for a 1.00a/r T4 twin scroll 6466 on an RB26 running Kelford 274/270 cams on E85:

And boost:

 

And a pretty much identical setup but with the cams dialled in for power instead of spool (so "laggy"):

 

 

We will also re-check the system, if there is any miss installation, leakage etc. to clarify that technically is everything okay. But it seems like that because for it's boost level it's in general not performing that bad. If the power comes, there is a lot of power for sure. It's just that you feel that until the 5k rpm mark is nearly nothing especially when you drive on serpentines, hillclimbs etc. It's always like you have to wait from a big nowhere when you shift down or up until it's responsive and serious accelerate again.

Here is the summary, please keep the eye on the red and blue line which is ending in the 612 horses. Not the one down to that. Thats how it actually works on the dyno.


 

5 hours ago, r32-25t said:

Have you tried smoke testing it to make sure there’s no leaks in the pressure system?

We did not try this yet. but it's also a good tip. Thank you.

Edited April 22, 2020 by meX

[BakemonoRicer]

Wow, that's laggier than my Nismo R1 turbos. I'm hitting 20 pound at 4.5k, this makes my car look like a response monster.

 

[feedmyfast]

8 hours ago, meX said:

I will speak to my friend and we will make another slight remap try with the OEM cams. May this helps a little bit and will also talk about that with the tuner again. Some people here are also mentioning that it's a point of optimization of the timing, so I'm going to ask them also.

Sorry for the Missunderstanding. I didn't mean that the tuner is not familiar with high horse power turbo applications. They are if its depending on a stock RB26, because they say, that the engine will probably/mabye break immidiately after tuning it in his stock. That's why they did it on 1.25 bars or 17-18 PSI.

My personal wish was to go for 1.7 Bars (~ 25 PSI) because there are still the stock valve springs in the head and to reach a good power target. But they did not go for because of the stock engine.

There are Injector Dynamics 1000cc injectors installed and R8 coils and also a Nismo Fuel Pump.
 

We will also re-check the system, if there is any miss installation, leakage etc. to clarify that technically is everything okay. But it seems like that because for it's boost level it's in general not performing that bad. If the power comes, there is a lot of power for sure. It's just that you feel that until the 5k rpm mark is nearly nothing especially when you drive on serpentines, hillclimbs etc. It's always like you have to wait from a big nowhere when you shift down or up until it's responsive and serious accelerate again.

Here is the summary, please keep the eye on the red and blue line which is ending in the 612 horses. Not the one down to that. Thats how it actually works on the dyno.


 

We did not try this yet. but it's also a good tip. Thank you.

Can you take a picture of the the boost table? Going by how you said the car drives either the ECU is targeting boost late in the RPM range or you have a boost leak which is causing a delay. 

 

As someone mentioned before I was running the Gen 2 6466 on a RB25 and boost ramp up was happening around 3-3.5K RPM. Tuning wise we targeted "MAX BOOST" during the ramp up to ensure the wastegate was completely closed.  With a better flowing RB26 head you should see boost at that time if not earlier. On one of my many dyno sessions my car was only seeing 25 lbs around 5K RPM. Come to find out I had a large leak around the IAC valve. These turbos are workhorses, they will build boost even with a sizeable leak.  

[33SOM]

On 22/04/2020 at 8:32 AM, KiwiRS4T said:

no-one is suggesting a return to twins s

I have a 6466 on my built 26. Twinscroll .84 rear. What should I expect to make on a 98ron tune? Not ready for e85 yet...

Made 400rwhp @10psi while running it in 2 years ago and I haven't been bothered to return to the dyno...

Happy to run all of the boost in the world

Cheers

[klutched]

For anyone interested in larger frame PTE's here's my 7685 Gen 1. 912rwhp on 33psi. Still have a little bit more boost to jam in it so we'll see how we go. Hoping to get up a bit closer to 960-980rwhp on the roller.

Setups is 26/30 3.4 stroker with a powerglide. 

[BK]

Nice work ? Were you not over 1000rwhp on a smaller Precision if I remember correctly ? How does the 7685 compare ?

[klutched]

15 minutes ago, BK said:

Nice work ? Were you not over 1000rwhp on a smaller Precision if I remember correctly ? How does the 7685 compare ?

Yeah we went 1021hp on 35psi with the 7175 gen 1 (thought it was a 7675). That was ok a hub dyno though. That old turbo was a menace it would come on pretty quick. New one definitely feels a little slower but I can't really compare because I changed the diff gears to 3.69s at the same time I put the 7685 in. 

First vid is 7685 we had 30psi ramping to 37psi at around 6250rpm (can hear when she starts singing), second vid is 7175 racing mates gtr with the 7685. On a mainline hub he spun up 1130hp 36psi. I think I raced him on 28psi because we couldn't run anymore due to wheel spin with what I assume is the major difference with 4.11s vs the 3.69s now. 

[meX]

On 4/22/2020 at 12:45 AM, Lithium said:

 

Have you done much investigation into problems with the car?   To me there is very likely to be something wrong, like cams installed wrong, or a major boost or exhaust leak.   Did you install the valve seat in the wastegate, for example?

 

Hey Lithium,

you were right; the car had some issues and there was a big leakage beginning from the intake manifold and some minor other points in the turbo system.
I think that was one of the main reasons why this thing was not working correct. If you have a leakage in 4 of 6 cylinders at the intake, its possible that it cannot work well, haha.

Anyways, after a frustrating work i changed the system. I just hope that i reach my targets and then it should be fine. This time, without leakage ?

 

Edited August 26, 2020 by meX

[Lithium]

8 hours ago, meX said:

you were right; the car had some issues and there was a big leakage beginning from the intake manifold and some minor other points in the turbo system.
I think that was one of the main reasons why this thing was not working correct. If you have a leakage in 4 of 6 cylinders at the intake, its possible that it cannot work well, haha.

Anyways, after a frustrating work i changed the system. I just hope that i reach my targets and then it should be fine. This time, without leakage ?

 

Cheers for coming back, and glad you've found stuff.  What did you change in the system?  Are you still on the same turbo/cams?  I'd say with the kind of things you have found it probably will be a different beast to drive using those same parts

[meX]

Yes it was a bit of "luck" in a "bad luck" situation (sorry don't know how to spell that correct in english :D).
First of all there was a destroyed water hose behind the idle control valve and under the intake manifold, which we had to fix.
After removing the manifold and idle control valve we saw, that there was a big leakage between the manifold of themselve and the throttle bodys. It was clearly to see on 4 of the 6 cylinders. Further there were 2 small hoses going to the front from the intake manifold (they were connected under the manifold) in which 1 of them was "blind" but not closed. So there was a leakage too.

Second step was removing the turbo system; turbo, manifold, wastegate & downpipe in which we also recognized a pretty small leakage at cylinder nr. 6 on the end but this was a minor leakage. 

Anyways, we fixed the water hoses and so on and reinstalled everything as it should be.
fter a few test drives with some different cars and a few sleepless nights like "thinking what should i do", i  decided to sell the current system and go back to a smaller one and different components.

I went for a 6 boost manifold and 2 turbo smart 40mm wastegates to have a "real" twinscroll system and a new downpipe. Hopefully that this system is now bringing the driving style what I want to have.
We also decided to keep the camshafts for first with the smaller turbo, to test the capability of them if they work or not. If the summary is not good at all, we will change the camshaft to OEM ones. It was a lot of work already and I dont wanted to put out the camshafts immidiately bevor testing them with the new turbo on the dyno and real life.

That's now the actual situation.
Let's see what happens.

Edited August 27, 2020 by meX

[r32-25t]

Has anyone in here used a 6870 with the H front cover on a 2.8? I’ve got the 6466 and have had a few people saying I should go up to the 6870 when the new engine goes in. 

[hattori hanzo]

I am at this same cross road, keen to see results of 2.8 6870

[BK]

7 hours ago, r32-25t said:

Has anyone in here used a 6870 with the H front cover on a 2.8? I’ve got the 6466 and have had a few people saying I should go up to the 6870 when the new engine goes in. 

Why ? What is your real goal with the car ? I feel if you go 6870 you're going down the road of a Coota car then you'll be saying why didn't I go a 7675 ?

6 hours ago, hattori hanzo said:

I am at this same cross road, keen to see results of 2.8 6870

So am I, but again why ? Has no one done a 6870 on a 2.8 in Oz ? Is your goal more lap time in WA tracks orientated or drag times ? If so on track isn't Simon R. still quicker with a 6262 on a 2.6 ? Don't get me wrong, but isn't stepping over a 6466 instantly compromising the car away from being well rounded drag, track, street and khana car into basically a "Coota style" top end only car ? And again if this is the case going to at least a 7675 is the answer rather than a 6870 ?

Obviously I have a genuine interest in this, as my Nitto 2.8 with a 6466 1.00 a/r T4 twin scroll will be finally tuned for power in the next 8 weeks after over 2.5 years of anticipation.

So I guess the question is, where some decent 6870 results are on an RB26 - post them up here !

[jet_r31]

Theres a world of difference between a 6870 and a 7675...

As soon as you step up to the 75mm turbine  its a lot lot lazier.. So i can understand if you said 7175 vs 7675.

The 70mm turbine  is still responsive like the 66mm turbine

7175 is where you start to get lazy

Edited April 30, 2021 by jet_r31

[BK]

6 minutes ago, jet_r31 said:

Theres a world of difference between a 6870 and a 7675...

As soon as you step up to the 75mm turbine  its a lot lot lazier.. So i can understand if you said 7175 vs 7675.

The 70mm turbine  is still responsive like the 66mm turbine

7175 is where you start to get lazy

Thanks for that mate. So there is some merit to the guys suggesting to maybe skip the 6466 stage in favour of the 6870 in the first place ? This was my original intention.

I know the 6870 will make more power, but surely that will translate into a slower car everywhere else but the strip ?