Jump to content
SAU Community

Recommended Posts

Do you mind telling me exactly what the setup you had previously was? I'm trying to find solid VE data for the RB engines and I'd like to use dynos (like yours) to determine where we are in terms of VE and turbo calcs and how this is applied. Using the defaults in Match-bot seems to make engines seem more responsive than they are in real life.

For your car and the first dyno posted, I came up with the following numbers so far: I simply can't get match-bot to work with your recorded boost, rpm, and power levels any other way than with these tweaked VE numbers, but they sure are close with these VE numbers! stretching from 72 out to 121 seems outlandish..but it makes the data fit and supports the maximum supported airflow of 68 lbs/min that this turbo is advertised at. I am assuming your engine had cams previously?

RPM - VE

3000 - 72

3500 - 72

4000 - 80

4500 - 100

5000 - 111

5500 - 117

6000 - 120

6500 - 121

7000 - 121

7500 - 118

8000 - 115

I do not know the effect that increasing stroke has on existing VE, but I sure would like to know. I'm hoping it increases at low rpms...because if not, Match-bot doesn't think much changes on the bottom end as far as boost threshold goes with these numbers. If you play with it, you will see that going up from 2.6L to 2.75L makes VERY little difference other than overall power. seems that VE drives a ton turbocharged HP calculations.

Sorry for attacking your thread with technical jargon, but I am trying to help you decide how much power you'll get out of the 8375. Sometimes going UP in displacement hurts efficienies, and resulting power. It may be better matched to a 2.6 or 2.75 than a 2.9

Edited by HarrisRacing
  • Like 1

I'm going for a very similar build. I guess I'm trying to figure out what cams and additional stroke do to VE tables for engines and I'm having trouble finding it all.

Hate to tell you but experience builds good engine combos not a computer program, there will be so many variables that the computer won't take into account that it will be never be accurate

Do you mind telling me exactly what the setup you had previously was? I'm trying to find solid VE data for the RB engines and I'd like to use dynos (like yours) to determine where we are in terms of VE and turbo calcs and how this is applied. Using the defaults in Match-bot seems to make engines seem more responsive than they are in real life.

For your car and the first dyno posted, I came up with the following numbers so far: I simply can't get match-bot to work with your recorded boost, rpm, and power levels any other way than with these tweaked VE numbers, but they sure are close with these VE numbers! stretching from 72 out to 121 seems outlandish..but it makes the data fit and supports the maximum supported airflow of 68 lbs/min that this turbo is advertised at. I am assuming your engine had cams previously?

RPM - VE

3000 - 72

3500 - 72

4000 - 80

4500 - 100

5000 - 111

5500 - 117

6000 - 120

6500 - 121

7000 - 121

7500 - 118

8000 - 115

I do not know the effect that increasing stroke has on existing VE, but I sure would like to know. I'm hoping it increases at low rpms...because if not, Match-bot doesn't think much changes on the bottom end as far as boost threshold goes with these numbers. If you play with it, you will see that going up from 2.6L to 2.75L makes VERY little difference other than overall power. seems that VE drives a ton turbocharged HP calculations.

Sorry for attacking your thread with technical jargon, but I am trying to help you decide how much power you'll get out of the 8375. Sometimes going UP in displacement hurts efficienies, and resulting power. It may be better matched to a 2.6 or 2.75 than a 2.9

Regardless of head, cams etc and all things being equal except for displacement, the larger motor will always produce more power everywhere in the curve than the smaller motor.

While a VE at a given RPM point may be lower, remember that VE is effeciency relative to volume being displaced. So while a VE may appear to be lower on the bigger motor for a certain RPM/Load point, it is still moving at least as much air as the smaller motor is for that same RPM/Load point.

Whether the engine is under boost or vacuum, more displacement per cylinder will equal more efficent cylinder filling. For a single rotation the larger motor is moving more gas. Without going into rod ratios or any of that other crap, this means a larger motor will pull more pressure differencial relative to the pressure inside the intake plenum than a smaller motor. If you do factor in rod ratios, the shorter rod ratio has benefits there for better cylinder filling too, due to faster acceleration of the piston away from TDC.

Even at the top end of the RPM range when the head is becoming a restriction to allowable airflow, and the power curve dropping off for the large engine will still be a higher output than a smaller motor would for that same RPM. Simply because it is moving more air through the restrictive ports than the smaller motor can, due to that increased pressure differential.

  • 3 weeks later...

Regardless of head, cams etc and all things being equal except for displacement, the larger motor will always produce more power everywhere in the curve than the smaller motor.

While a VE at a given RPM point may be lower, remember that VE is effeciency relative to volume being displaced. So while a VE may appear to be lower on the bigger motor for a certain RPM/Load point, it is still moving at least as much air as the smaller motor is for that same RPM/Load point.

Whether the engine is under boost or vacuum, more displacement per cylinder will equal more efficent cylinder filling. For a single rotation the larger motor is moving more gas. Without going into rod ratios or any of that other crap, this means a larger motor will pull more pressure differencial relative to the pressure inside the intake plenum than a smaller motor. If you do factor in rod ratios, the shorter rod ratio has benefits there for better cylinder filling too, due to faster acceleration of the piston away from TDC.

Even at the top end of the RPM range when the head is becoming a restriction to allowable airflow, and the power curve dropping off for the large engine will still be a higher output than a smaller motor would for that same RPM. Simply because it is moving more air through the restrictive ports than the smaller motor can, due to that increased pressure differential.

Perhaps I was unclear.

Your logic keeps the assumption that the turbo isn't at it's max limit. I was studying match-bot when looking at my stroker and made the realization that these new "billet" wheels are adding airflow on top end and in Joey's case I would absolutely recommend him change the compressor wheel and let me explain why.

His cast wheel 8375 is only rated for 68 lbs/min of airflow. Any more than that and it's horribly inefficient and/or at overspeed (dangerous for turbo) and I'm sure is not recommended by BW engineers.

So using his old 2.6L setup (and some VE numbers I have reverse engineered), the match-bot for top end is as follows:

6000, 21 psi, 58 lbs/min, 542 HP

6500, 21 psi, 63.5 lbs/min, 570 HP

7000, 21 psi, 68 lbs/min, 600 HP (Max flow reached)

7500, 19.5 psi, 68 lbs/min, 592HP (max flow held, dropping boost)

8000, 18.5 psi, 68 lbs/min, 542 HP (boost still dropping to maintain max flow)

8500, 18.5 psi, 66.8 lbs/min, 488 HP

So this, to me, is a GREAT street turbo for a pumpgas 2.6L setup. It's sustaining boost to pretty dang high rpm levels and is just at the edge of the compressor map.

Data here

Now the SAME turbo on his new 2.9L:

6000, 21 psi, 65 lbs/min, 602 HP

6500, 19.5 psi, 68 lbs/min, 607 HP (max flow reached, dropping boost to stay on map)

7000, 17.5 psi, 68 lbs/min, 606 HP (Max flow held, still dropping boost)

7500, 16 psi, 68 lbs/min, 594.5 HP (max flow held, dropping boost)

8000, 14.5 psi, 68 lbs/min, 535 HP (max flow held, dropping boost)

8500, 14.5 psi, 66.8 lbs/min, 482 HP

So here you see that at 8000-8500 rpms the 2.9L is actually making LESS horsepower than the 2.6L at the SAME airflow limitations (turbo limits) This is because the turbo is falling off of the map at overspeed and I have to drop the boost to keep it in the safe zone.

Data here

Now the 61.4mm FMW wheel in his existing turbo on his new 2.9L:

6000, 21 psi, 65 lbs/min, 604 HP

6500, 21 psi, 70.6 lbs/min, 634 HP

7000, 21 psi, 76 lbs/min, 670 HP

7500, 20.5 psi, 78 lbs/min, 678 HP (boost lowered, max flow reached)

8000, 19.5 psi, 79 lbs/min, 622 HP (boost lowered, max flow held)

8500, 19.5 psi, 77 lbs/min, 561 HP (boost sustained, max flow dropped)

This is why I suggested that Joey look into changing out the cast wheel for the FMW 61.4mm compressor and housing that is found in the EFR turbo. This will allow his 2.9L to still be on the map on top end (thus making 30-80 HP more from 6500-8500 rpm over his existing cast 8375) since the FMW wheel limit is 79 lbs/min and loses NOTHING to the 8375 on bottom end with the turbine choices offered (hence why the billet wheels are slowly taking over).

Data here

I hope this helps clear up what I was getting at.

Patrick

PS - I would LOVE to see actual dyno results from this swap Joey!

Edited by HarrisRacing
  • Like 1

But I wanted to add...

My math all assumes that the increased stroke (and resultant piston acceleration speed per rpm), doesn't affect the VE table. This was the original question I had and lots of internet searching still didn't provide an answer. So yes, you do get more displacement, which should technically help everywhere, but what if the increased piston speed (vs. standard stroke) reduces VE at high rpms? Then effectively you've almost just moved the power band to the left (good thing really) and let the increased displacement of the stroke help in the bottom and mid rpm range (which again I like on a streetcar), yet lost a little VE at top end (which I agree still should make more HP).

Edited by HarrisRacing

Interesting, thanks for the post mate, obviously a computer isnt 100% correct but I see what your getting at.

Must remember One of the benefits of the stroker is that I do not need to spin it to 8500 anymore as the power and torque band is now wider and boost comes on earlier. Also cam gears will be dialled in for response so it will actually fall over quicker which is fine as I won't be spinning it much past 7500. Good for reliability :D

I wasn't aware that its a straight swap for the FMW wheel!??

and a back to back would be great! I'm just sick of spending money is all. I also have the option of going to a larger rear housing which would allow boost levels past 25psi.

But let's see what the final result is, it didn't really fall over too much on the last tune and there is a few things I have done to help improve flow..

Time will tell!

Interesting, thanks for the post mate, obviously a computer isnt 100% correct but I see what your getting at.

Must remember One of the benefits of the stroker is that I do not need to spin it to 8500 anymore as the power and torque band is now wider and boost comes on earlier. Also cam gears will be dialled in for response so it will actually fall over quicker which is fine as I won't be spinning it much past 7500. Good for reliability :D

I wasn't aware that its a straight swap for the FMW wheel!??

and a back to back would be great! I'm just sick of spending money is all. I also have the option of going to a larger rear housing which would allow boost levels past 25psi.

But let's see what the final result is, it didn't really fall over too much on the last tune and there is a few things I have done to help improve flow..

Time will tell!

I think it is just the FMW wheel and front compressor cover. I think both of these parts are relatively cheap (likely less than $200 total).

You know (based on our previous conversations here) that I was leaning toward the 8375 cast for my build as well since they are $600 US and they would be a great bottom end pump gas setup for a stroker build. I did go overboard on the 8374 EFR simply because I picked one up for $1700 US shipped and the financials just work after pricing in wastegates, FMW turbo, etc. Bad thing is I'm stuck with the .92 IWG housing now unless they release different IWG A/Rs in the future.

Edited by HarrisRacing

Why don't you change rear housings? I'm sure somethring could be worked out.

After being in a stock 2.6 with a 8374 1.05 AR rear, I'm not sure if the 0.92 is necessary. Definately not on a stroker IMO.

Why don't you change rear housings? I'm sure somethring could be worked out.

After being in a stock 2.6 with a 8374 1.05 AR rear, I'm not sure if the 0.92 is necessary. Definately not on a stroker IMO.

Tell us more!! Wait...do more...get us video!!!

Why don't you change rear housings? I'm sure somethring could be worked out.

After being in a stock 2.6 with a 8374 1.05 AR rear, I'm not sure if the 0.92 is necessary. Definately not on a stroker IMO.

I'm going for a similar setup to Joey's...bottom end monster. I like the simplicity of the IWG model instead of 2x external gates, dumps, etc. The excessive "Octopus humping a hair dryer" under the hood just wasn't what I was going for on my car.

I'm going for a similar setup to Joey's...bottom end monster. I like the simplicity of the IWG model instead of 2x external gates, dumps, etc. The excessive "Octopus humping a hair dryer" under the hood just wasn't what I was going for on my car.

so really your not going similar setup. Just a stroked bottom end

so really your not going similar setup. Just a stroked bottom end

I was referring to the small(ish) cams, stroker, smaller AR turbine, etc. Looking for nice street powerband. I would say I'm heading in the right track as opposed to super-high-revving. long-duration-cammed, 2.6L. And I don't like the RB30 block idea with the taller deck, etc with the funky fitment issues.

  • 3 months later...

So engine has been in for a couple of months now, a few issues needed addressing such as fuel pumps and making a few other things fit

Everything is hooked up and ready for tuning,

Also fitted the AO rear brembos

post-47556-0-81369700-1440585353_thumb.jpgpost-47556-0-07073400-1440585397_thumb.jpg

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • For these last 7 years of ownership, I've always had to use a small scissor jack under one of the front tow hooks to raise the front just enough so my low-profile jack fits under to reach my subframe jack point. I'm beginning to get annoyed of always having to do this. Are there any lower low-profile jacks that fit under the gtr lip on a dropped car?
    • Seat of the pants assessment of the new intake: The car is way less "doughy" when hitting the loud pedal, especially off idle when stopped or in traffic, I did use a cheapo lazer thermal thingo to measure the temp around where the pod filter got its air, it was between 55 - 60°C, in saying this the car was shut off and not moving, so the OEM intake pipe was not supplying any fresh air to where the pod was when the car was at least moving A weird bonus was induction noise on the throttle in the cabin increased a bit,  I was worried that I was actually going to lose some of that induction noise I love so much, outside though, when I got the daughter to do a WOT drive by pass for me, the induction noise has increased alot when on the throttle, not quite ITB doort, but well up there I'm extremely happy with the results and have been exploring the country roads in the region  As for house mods: 1.New front fence is up and is awesome, it really upgraded how the joint looks from the street, and the added security is nice 2. Electricians have replace some interior lights, and with more lighting in the garage, a few new motion detecting lights out the front above the garage, front room, and at the front door, which I have already found heaps helpful coming and going, also now has fancy pants CCTV all round the house The only hold point for power though is the solar and batteries due to supply issues, although this will happen over the next few weeks 3. I have done a heap of landscaping out the front and I'm almost ready to do a new small retaining wall with some nice blocks to replace the brick and cemented in rocks around the raised garden beds cemented in river stone "was the fashion at the time" the house was built. I currently have a pallet of retaining wall blocks and 2 bulka bags of 20mm blue metal to replace the wood chip that is in the raised garden beds around the house 4. I now have 3 big raised garden beds for out the back to grow some vegetables, about 70cm high, 200cm long and 100cm wide 5. My 2 compost bins are already pretty full with brown, green and kitchen waste from the landscaping I'vedone so far, but they will probably take a few months to break down, so anything else that gets chopped, trimmed, and kitchen waste will just start filling the base of the raised garden beds to about 30cm before I start throwing 40cm of good compost, and stuff, for the vegetables to grow in, I'll need a few ton of compost and soil, but the local supplier can sent me bulka bags of the stuff Basically the logs, wood chips and a few strategically placed rocks for drainage, will give the beds some good organic materials down low to break down over time, and they will hold moisture during the warmer months to save the water in my big arse water tank if we don't get alot of rain So, all in all, the car and house mods are going well, and I'm really enjoying being retired, I sleep in too 0700 and slowly plod around inside until I feel like actually doing anything, and only work in the yard for as long as want, which has actually been alot over the last few weeks,  although when you look at it, it seems that not a huge amount of work has been done,  until I look at the before I started the work pics Happy days and good times indeed 
    • hahaha yeah. Plan is to get side skirts and probably just rear pods. But going to do them one-by-one. I've got a set that I really like from RHDJapen, but that one isn't shipped to AU. So need to find someone who can get it for me
    • Here's an idea, answer the questions I asked you as they are trying to work out WHY the LSD will be binding up in a straight line.
×
×
  • Create New...