433 replies to this topic

[1cobrav8]

Hi Frank, that’s some good figures from a pretty much stock b207? Do you know what size rotrex he is running?

[1cobrav8]

Sorry I’ve just gone back and seen he’s in a c38-71

[Nev]

Hi Frank, that’s some good figures from a pretty much stock b207? Do you know what size rotrex he is running?

 

B207 = dirt cheap power, it surprises me that more Z22SE engined people don't use them, their form factor is very close to the OEM engine.

Edited by Nev, 02 December 2018 - 02:16 PM.

[alexb]

It's a C38-61. Engine is almost stock: ported head (like the Harrop guys), stage 2 blower cams, ZZP valve springs, JE pistons, forged rods and custom (local machine shop) sleeves. TBH, I'm not sure if any of that is required, except for porting the head. I run the Rotrex such that it reaches it's max RPM at 7.500 engine RPM. The -71 and -81 will also work with the B207. The -91/92 is more for bigger engines.

[1cobrav8]

It's a C38-61. Engine is almost stock: ported head (like the Harrop guys), stage 2 blower cams, ZZP valve springs, JE pistons, forged rods and custom (local machine shop) sleeves. TBH, I'm not sure if any of that is required, except for porting the head. I run the Rotrex such that it reaches it's max RPM at 7.500 engine RPM. The -71 and -81 will also work with the B207. The -91/92 is more for bigger engines.

It’s a great result really. Have you had any issues with the build at all? Did I translate it. Orrectly rhat youbare running a peak boost pressure of 1.6bar? I plan to build a 2.35 using a 2.2 crank and sleeved 89mm block with the c38-91/92. My cams Are catcams 277deg with 10.75mm lift. I plan to hit around 530bhp@8000rpm.

I don’t suppose you have the ability to easily make another Rotrex bracket? Or supply a drawing?

[alexb]

Yes, peak is about  1.5 - 1.6 bar. I didn't do any fine tuning yet and it turned out that I was using the wrong narrow band lambda sensor, which OBDTuner doesn't like. No real issues with the build, just the usual trial and error. Beware that even with a 2.35L you will need significant boost to get to 530bhp. The C38-91/92 seems to be made for high flow, low boost. A -81 might be the better choice. No drawings of the bracket, was not that difficult tbh. I found a 200x200x10 mm piece of L-shape construction steel and made it from that. First did a prototype using easier materials. I borrowed an old C38-61 from the local Rotrex dealer and was glad I did, because of the number of times the thing got mounted and unmounted.

 

For the build you're planning, if possible use an 8PK belt drive. I use 6PK. If you look at the PK specs, it will not handle the power requirements. For my set up I assume 40-50 hp for the Rotrex. In practice, the belt drive is fine. It may require frequent belt changes, but that can be done in less than a minute. But for 530bhp, you're really going to push it. One other thing is the BOV or BOV's, as the Rotrex flow will only depend on RPM and not on engine load. You need to get rid of a lot of air when you're just cruising. I had the BOV's -I use two standard VAG ones- blow to ambient at first and it's loud. Great when you accelerate and they blow off when you switch gear, but just bloody annoying when you're cruising. Plan to feed them back to the intake after the filter.  

 

530Bhp will be mental 

[1cobrav8]

I’ll be honest one thing I am worried about is getting really frustrated with the constant BOV noise, I’ll be keen to hear you feed back after you’ve fed them back into the intake system.

Are you still running the base map from Peter? What sort of ignition figures are you using at WOT? I will certainly give the blower size some more serious thought and planning before ordering. It was TTS hear on the UK who suggested the c38-91 for what I want to achieve, but I will run this by them again nearer the time.

What’s you target bhp?

[alexb]

I have fed the BOV's back into the intake. Noise not an issue anymore. Got a base map from Peter and did a couple of fuel learning sessions before realizing the primary lambda sensor is not an NGK. The wide band and the narrow band kept on indicating a small difference in lambda values. Changed the bung the wide band sensor is in, changed the wide band, all the time fully convinced the narrow band was an OEM one. Then finally checked the narrow band and found it to be a Delphi and not NGK. Everything spot on now. Didn't change ignition at all. Might do so in the future, but want to drive it a bit before diving in again.

 

I started with a 350Bhp target, but soon realized it might be a little more as I was being conservative with a number of things. 400 Was a nice surprise. Issue is that you never know until you try. I'm not sure what the bottleneck is right now. One thing is that the exhaust backbox is my own design, using two expansion chambers instead of the usual absorption type. 3" All the way, but I don't know what the back pressure is, so don't know if that will be the bottleneck. 

[Exmantaa]

Hi Frank, that’s some good figures from a pretty much stock b207? Do you know what size rotrex he is running?

 

Think he has a C38-61.

Edit; too late...

 

It's a centrifugal, so power comes in at higher rpm's. I sketched our 2.0 Harrop curve in his power plot there and the Rotrex starts to shine above 6000rpm. 

 

 

Edited by Exmantaa, 03 December 2018 - 11:14 AM.

[1cobrav8]

 

Hi Frank, that’s some good figures from a pretty much stock b207? Do you know what size rotrex he is running?

 

Think he has a C38-61.

Edit; too late...

 

It's a centrifugal, so power comes in at higher rpm's. I sketched our 2.0 Harrop curve in his power plot there and the Rotrex starts to shine above 6000rpm. 

 

 

I saw that frank....very interesting. I think the potential in Alex's build is very good, especially if he is still just running peters stock ignition map which is usually around 17deg at WOT. i would plan to introduce some more low down boost if possible with the bigger supercharger and possibly smaller pulley. But i need to what out all the max charger speeds etc to ensure I don't over spin it at 7800-8000rpm. 

[Exmantaa]

 

 

It’s a great result really. Have you had any issues with the build at all? Did I translate it. Orrectly rhat youbare running a peak boost pressure of 1.6bar? I plan to build a 2.35 using a 2.2 crank and sleeved 89mm block with the c38-91/92. My cams Are catcams 277deg with 10.75mm lift. I plan to hit around 530bhp@8000rpm.

 

The Rotrex will shine at higher rpm's, but not sure if 8000rpm with the 2.2 crank (94.6mm stroke) is wise... 

Make a 89mm 2.14l  screamer?

 

(not sure why you want >500hp in a VX, but cooling it will be you main problem.)

 

(ps2; what about a turbo build?)

Edited by Exmantaa, 03 December 2018 - 11:44 AM.

[Rosssco]

A24NFT (with gen 2 88mm block and crank) build would be a thing..

 

And very drivable given a suitably sized turbo (one of the smaller EFR units). The torque might destroy everything though.

[FLD]

Have you considered the geared rotrex? Should solve the low end issues.

[1cobrav8]

 

 

 

It’s a great result really. Have you had any issues with the build at all? Did I translate it. Orrectly rhat youbare running a peak boost pressure of 1.6bar? I plan to build a 2.35 using a 2.2 crank and sleeved 89mm block with the c38-91/92. My cams Are catcams 277deg with 10.75mm lift. I plan to hit around 530bhp@8000rpm.

 

The Rotrex will shine at higher rpm's, but not sure if 8000rpm with the 2.2 crank (94.6mm stroke) is wise... 

Make a 89mm 2.14l  screamer?

 

(not sure why you want >500hp in a VX, but cooling it will be you main problem.)

 

(ps2; what about a turbo build?)

 

@8k the piston speed would be just over 25m/s which is the maximum I would be comfortable with....so in short I agree it's on the edge but if you don't try you don't know. 

 

And yep I've thought about a turbo many times as I could then have pretty much whatever power I want but I like the simplicity of a supercharger and the way they drive. I think my current car with the power of my last one would be a pretty good setup. The rotrex dropping a little mid range torque would most likely just aid the drivabilty on track and road. 

[vocky]

A24NFT (with gen 2 88mm block and crank) build would be a thing..

 

funny you should mention that, I am slowly collecting parts

[Rosssco]

 

A24NFT (with gen 2 88mm block and crank) build would be a thing..

 
funny you should mention that, I am slowly collecting parts

 

 
I can't imagine you building a turbo engine for your own consumption (maybe in another Vauxhall?)

[vocky]

 

 

A24NFT (with gen 2 88mm block and crank) build would be a thing..

 
funny you should mention that, I am slowly collecting parts

 

 
I can't imagine you building a turbo engine for your own consumption (maybe in another Vauxhall?)

 

for my other car

[1cobrav8]

Finally got round to fitting the header tank that Joe supplied tonight, I got it powder coated black along with the intake pipe. I also sent some measurements to a friend of mine to see what can be done with regards to boring the Gen3 block 😏

[FLD]

Does the cylinder have the step on the outside of the alu part like the gen 2? It looks a lot more robust! Not surprising given it's pattern sand cast rather than lost foam but it does look chunky.

[1cobrav8]

Front end collected from the paint shop and started to test fit it. So far so good, just need to wait for the black bolts to arrive for the front grills now really.....



Lee dropped down a steinmitz grill when he came on the dyno a while back as I wasn’t sure whether I’d use it or not. Well I’ve decided to lol. I’ve made two brackets to hold the grill in place(will be painted black). There on rivnuts so just four bolts and the grill pops out. I’m hoping with this grill being less restrictive and the rad all now being fully sealed the cooling should be much better. I also put a foam strip between the two front rads to stop heat transfer