Righthand drive Z4M – SuperSprint V1 stepped headers and Severn tune (dynos and data logging)

[///MBan]

Hi all,

**sorry for cross-posting: this is also on ZPost**

This post got a bit longer than I intended, so here’s an executive summary:
- The SuperSprint V1 stepped headers marketed as being for right-hand drive cars do not fit without modification
- Despite the modifications need to get the headers to fit, they still made more top end power before tuning
- Josh from Severn Tuning (Pokeybritches on the forums) provided excellent support and customisation for my tune, resulting in gains in the order of 10% power and torque over large sections of the rev range
- The gains on the dyno seem to be reflected during data logging in real-world conditions
- The tone of the exhaust has changed a bit, with more ‘fizz’ evident but not what I would call unpleasant rasp.

For reference, I have a ‘Euro spec’ Z4M, with the better (cat-less) headers and S-pipe. I bought the V1 stepped headers and S-pipe with HJS catalytic converters a while ago but only just got around to having them installed… unfortunately, the installation didn’t go to plan as the rear bank did not clear the steering shaft. I had the option at that stage to send them back to SuperSprint in Italy but since I had already paid to have the stock headers taken off and to have the SuperSprint headers ceramic coated, I thought I would have the workshop modify them and see what happens. Pictures below of the clearance issue and the workshops modification.

IMG_8158_SML.jpg (122.6 KiB) Viewed 1507 times

IMG_8164_SML.jpg (124.97 KiB) Viewed 1507 times

IMG_8213.JPG (111.25 KiB) Viewed 1507 times

Josh from Severn Tuning supplied three tunes to test with the headers: one ‘best’ guess (Tune 1) and then two with Vanos changes to see where some more gains could be found.

The workshop ran the car on the dyno with stock everything (my car has no other modifications besides a set of lightweight wheels) but due to the modifications to the headers and the workshop’s other jobs, as well as sending the headers back for re-ceramic coating, it was then about three weeks before the post-header installation runs. As a result, I’m not sure how comparable the results are.

All runs except for the stock one were done on the same day with the car left strapped to the dyno.

The first chart below shows all runs at the same time, which is pretty messy.

Below that is a dyno chart of stock versus Tune 1. Tune 1 was best overall but Tune 2 and 3 were better at high revs. With the stock tune, the headers made more power than stock in the high end and a bit more down low but were worse through the mid-range. So, the headers definitely need a tune to get the most gains.

2021 Mar - headers and 3 tunes_SML.jpg (141.4 KiB) Viewed 1507 times

2021 Mar - stock vs headers and tune 1_SML.jpg (136.99 KiB) Viewed 1507 times

I then took the car home and did some data logging for all three Severn tunes at an off-street location that allows a full third gear run. I sent the dyno charts and data logs to Josh, who then developed a couple of fine-tuned maps, resulting in Tune 6. I took the car back to the dyno and ran Tune 6 against the stock tune. In hindsight, it would have been good to also run Tune 1 on the same day but given it takes 50 minutes to load each tune, it just wasn’t feasible. The first dyno chart below is completely stock vs Tune 6 (done nearly a month apart) and the second is comparing stock tune (with headers installed, obviously) and Tune 6 (done on the same day with car kept strapped to the dyno). I was expecting Tune 6 to perform a bit better but when I compared the two stock tune with headers runs (one week apart) as a rough internal control, the readings were down on the second day, perhaps indicating that Tune 6 would have put up better numbers if it was run on the same day as Tunes 1-3. I’m not really sure why that would be but if nothing else it shows that comparing dyno runs from different days is pretty tricky. I didn’t get a dyno print out comparing the SS headers with stock tune over the two different days, but I did enter the data in MS Excel to create a chart (Tune 6 also included for reference). See below.

2021 Mar - stock vs headers and tune 6_SML.jpg (120.72 KiB) Viewed 1507 times

2021 Mar - headers vs headers with tune 6_SML.jpg (131.74 KiB) Viewed 1507 times

Stock tune with headers x 2 plus Tune 6.jpg (33.63 KiB) Viewed 1507 times

Finally, some third-gear data logging. The first chart below shows the MAF signal for the car when it was completely stock (on a slightly hotter day), compared to Tune 6. It looks like these data reflect the dyno results, with Tune 6 pulling in quite a bit more air than the stock run in the low and high rev ranges with the advantage being a little less clear around 4,500 – 5,500 rpm. Josh stated that MAF signals are not reliable enough for tuning, so they also may not be reliable enough to draw many conclusions. The second chart below shows the difference between the stock car and Tune 6 for distance covered over time. Again, not sure how reliable it is to take this information from the data logs but the stock runs were all pretty similar and the runs for Tune 6 all covered more distance than stock in the same time. The result is that over a third-gear run (approximately 10 seconds) the car with headers and S-pipe with a Servern tune covered 5.5m more than the stock car.

MAF reading - Stock vs Tune 6.jpg (41.49 KiB) Viewed 1507 times

Distance travelled - stock vs T6.jpg (31.41 KiB) Viewed 1507 times

Subjectively, the car feels really strong, particularly from 5,000 rpm but the low rev range also feels super sharp now. Sound-wise, the volume hasn’t changed much but it does ‘fizz’ a bit more. I think the ‘fizz’ is rasp that is damped by the stock X-pipe and rear mufflers but I actually quite like it and I’m not a fan of rasp. The intake sound is now less audible from inside, which is a downside in my opinion.

I’m super happy with the Severn tune and Josh’s support. I would recommend him in a heartbeat. The headers were a pain and I wonder how much (if any) power and torque was lost through adding the notches to the two primary pipes. Obviously, the whole thing cost more as well. SuperSprint, to their credit, took the product off their website as soon as I let them know. Still, I’d prefer that they headers fitted.

[GT Spec]

Hi all,

**sorry for cross-posting: this is also on ZPost**

This post got a bit longer than I intended, so here’s an executive summary:
- The SuperSprint V1 stepped headers marketed as being for right-hand drive cars do not fit without modification
- Despite the modifications need to get the headers to fit, they still made more top end power before tuning
- Josh from Severn Tuning (Pokeybritches on the forums) provided excellent support and customisation for my tune, resulting in gains in the order of 10% power and torque over large sections of the rev range
- The gains on the dyno seem to be reflected during data logging in real-world conditions
- The tone of the exhaust has changed a bit, with more ‘fizz’ evident but not what I would call unpleasant rasp.

For reference, I have a ‘Euro spec’ Z4M, with the better (cat-less) headers and S-pipe. I bought the V1 stepped headers and S-pipe with HJS catalytic converters a while ago but only just got around to having them installed… unfortunately, the installation didn’t go to plan as the rear bank did not clear the steering shaft. I had the option at that stage to send them back to SuperSprint in Italy but since I had already paid to have the stock headers taken off and to have the SuperSprint headers ceramic coated, I thought I would have the workshop modify them and see what happens. Pictures below of the clearance issue and the workshops modification.

IMG_8158_SML.jpg
IMG_8164_SML.jpg
IMG_8213.JPG

Josh from Severn Tuning supplied three tunes to test with the headers: one ‘best’ guess (Tune 1) and then two with Vanos changes to see where some more gains could be found.

The workshop ran the car on the dyno with stock everything (my car has no other modifications besides a set of lightweight wheels) but due to the modifications to the headers and the workshop’s other jobs, as well as sending the headers back for re-ceramic coating, it was then about three weeks before the post-header installation runs. As a result, I’m not sure how comparable the results are.

All runs except for the stock one were done on the same day with the car left strapped to the dyno.

The first chart below shows all runs at the same time, which is pretty messy.

Below that is a dyno chart of stock versus Tune 1. Tune 1 was best overall but Tune 2 and 3 were better at high revs. With the stock tune, the headers made more power than stock in the high end and a bit more down low but were worse through the mid-range. So, the headers definitely need a tune to get the most gains.
2021 Mar - headers and 3 tunes_SML.jpg
2021 Mar - stock vs headers and tune 1_SML.jpg

I then took the car home and did some data logging for all three Severn tunes at an off-street location that allows a full third gear run. I sent the dyno charts and data logs to Josh, who then developed a couple of fine-tuned maps, resulting in Tune 6. I took the car back to the dyno and ran Tune 6 against the stock tune. In hindsight, it would have been good to also run Tune 1 on the same day but given it takes 50 minutes to load each tune, it just wasn’t feasible. The first dyno chart below is completely stock vs Tune 6 (done nearly a month apart) and the second is comparing stock tune (with headers installed, obviously) and Tune 6 (done on the same day with car kept strapped to the dyno). I was expecting Tune 6 to perform a bit better but when I compared the two stock tune with headers runs (one week apart) as a rough internal control, the readings were down on the second day, perhaps indicating that Tune 6 would have put up better numbers if it was run on the same day as Tunes 1-3. I’m not really sure why that would be but if nothing else it shows that comparing dyno runs from different days is pretty tricky. I didn’t get a dyno print out comparing the SS headers with stock tune over the two different days, but I did enter the data in MS Excel to create a chart (Tune 6 also included for reference). See below.

2021 Mar - stock vs headers and tune 6_SML.jpg
2021 Mar - headers vs headers with tune 6_SML.jpg
Stock tune with headers x 2 plus Tune 6.jpg

Finally, some third-gear data logging. The first chart below shows the MAF signal for the car when it was completely stock (on a slightly hotter day), compared to Tune 6. It looks like these data reflect the dyno results, with Tune 6 pulling in quite a bit more air than the stock run in the low and high rev ranges with the advantage being a little less clear around 4,500 – 5,500 rpm. Josh stated that MAF signals are not reliable enough for tuning, so they also may not be reliable enough to draw many conclusions. The second chart below shows the difference between the stock car and Tune 6 for distance covered over time. Again, not sure how reliable it is to take this information from the data logs but the stock runs were all pretty similar and the runs for Tune 6 all covered more distance than stock in the same time. The result is that over a third-gear run (approximately 10 seconds) the car with headers and S-pipe with a Servern tune covered 5.5m more than the stock car.

MAF reading - Stock vs Tune 6.jpg
Distance travelled - stock vs T6.jpg

Subjectively, the car feels really strong, particularly from 5,000 rpm but the low rev range also feels super sharp now. Sound-wise, the volume hasn’t changed much but it does ‘fizz’ a bit more. I think the ‘fizz’ is rasp that is damped by the stock X-pipe and rear mufflers but I actually quite like it and I’m not a fan of rasp. The intake sound is now less audible from inside, which is a downside in my opinion.

I’m super happy with the Severn tune and Josh’s support. I would recommend him in a heartbeat. The headers were a pain and I wonder how much (if any) power and torque was lost through adding the notches to the two primary pipes. Obviously, the whole thing cost more as well. SuperSprint, to their credit, took the product off their website as soon as I let them know. Still, I’d prefer that they headers fitted.

Thanks for the detailed write up Shame that you had to modify the Supersprint headers. What was the Supersprint part number out of interest? I have just ordered a RHD set under part number 789801

[abar121]

What a great result and an absolutely brilliant write up!

Thanks for posting.

[///MBan]

Thanks for the detailed write up Shame that you had to modify the Supersprint headers. What was the Supersprint part number out of interest? I have just ordered a RHD set under part number 789801

Hi,

It looks like you have ordered the V2 stepped headers, whereas I bought the V1 (044931). I think the V2 don’t step out as much at the final merge so they can join to the standard s-pipe but I’m not sure if there are any differences between the primary pipe location.

You could contact SuperSprint to ask? They offered to pay to courier the headers back to Italy, so you may not be out of pocket if you already have the parts.

It is possible that SuperSprint sent me the LHD headers by mistake (there is no product number on the headers themselves), in which case your headers (and V1s) could be fine. Identifying a mix up in products could only be checked by putting two sets side by side. However, the shop that did the install mentioned they had previously seen the same problem with the V1 stepped headers, which doesn’t support that possibility.

[Darkangelv2]

Looks like your workshop did a great job with the modification

Is there room to cut the header opposite the hole already made and add a 'bulge' to maintain inner diameter? Or is there no room there?

[Pbondar]

Out of interest, does the dyno used purport to represent BHP at the crank or at the rear wheels?

[TomK]

Out of interest, does the dyno used purport to represent BHP at the crank or at the rear wheels?

Seriously? Yeah because a tuned S54 is really going to have lost about 70hp in 15 years
It's not "purporting" anything, unlike tuners seem to have a habit of doing in the uk and make up driveline losses for themselves to make the paying 'map' customer feel better.
It is measuring the actual wheel horsepower, the finite numbers make no difference really anyway, it is about seeing the change. It's not a willy waving contest.

I have just ordered a RHD set under part number 789801

Be interested to hear how you get on. The OE headers are pretty decent, for the cost I was thankful when I looked a couple of years ago there were no RHD header options! If they have sorted it out I might take another look one day.

[Pbondar]

Out of interest, does the dyno used purport to represent BHP at the crank or at the rear wheels?

Seriously? Yeah because a tuned S54 is really going to have lost about 70hp in 15 years
It's not "purporting" anything, unlike tuners seem to have a habit of doing in the uk and make up driveline losses for themselves to make the paying 'map' customer feel better.
It is measuring the actual wheel horsepower, the finite numbers make no difference really anyway, it is about seeing the change. It's not a willy waving contest.

I have just ordered a RHD set under part number 789801

Be interested to hear how you get on. The OE headers are pretty decent, for the cost I was thankful when I looked a couple of years ago there were no RHD header options! If they have sorted it out I might take another look one day.

Whoa, attitude, you need to take a chill pill..

There was no insinuation or snide comments..I was interested in the OP's progress..

I fully realise having done a few dyno runs that its the difference seen on one dyno ideally, corrected to ISA standards if run at different times that shows what's happened.

Did someone piss on your dreams or are you just being unpleasant?

[TomK]

I was interested in the OP's progress..

How so exactly? Why would whether it was wheel or crank horsepower come into that equation?

Did someone piss on your dreams or are you just being unpleasant?

Neither, I was just surprised at the ridiculous question and also just a bit bored of seeing the myriad of posts about how your 'mapped' n20 is a match for a 30i or whatever so I thought I'd stick my oar in, ok?

[Pbondar]

I was interested in the OP's progress..

How so exactly? Why would whether it was wheel or crank horsepower come into that equation?

Did someone piss on your dreams or are you just being unpleasant?

Neither, I was just surprised at the ridiculous question and also just a bit bored of seeing the myriad of posts about how your 'mapped' n20 is a match for a 30i or whatever so I thought I'd stick my oar in, ok?

Oooh we are feeling tetchy this afternoon aren't we?

Ref the dyno, its not a version I'd seen so a perfectly reasonable question to ask IMHO..

I think you'll find that compared to a "30i or whatever" my 'mapped' N20 is considerably faster rather than being a 'match'

Not sure what I've done to upset you but you can of course block people's posts if you don't like what they are saying

[GT Spec]

Thanks for the detailed write up Shame that you had to modify the Supersprint headers. What was the Supersprint part number out of interest? I have just ordered a RHD set under part number 789801

Hi,

It looks like you have ordered the V2 stepped headers, whereas I bought the V1 (044931). I think the V2 don’t step out as much at the final merge so they can join to the standard s-pipe but I’m not sure if there are any differences between the primary pipe location.

You could contact SuperSprint to ask? They offered to pay to courier the headers back to Italy, so you may not be out of pocket if you already have the parts.

It is possible that SuperSprint sent me the LHD headers by mistake (there is no product number on the headers themselves), in which case your headers (and V1s) could be fine. Identifying a mix up in products could only be checked by putting two sets side by side. However, the shop that did the install mentioned they had previously seen the same problem with the V1 stepped headers, which doesn’t support that possibility.

Just had confirmation from Supersprint that the 789801 headers are compatible with RHD. Will be starting a build thread so will post up the results

[///MBan]

Thanks for the detailed write up Shame that you had to modify the Supersprint headers. What was the Supersprint part number out of interest? I have just ordered a RHD set under part number 789801

Hi,

It looks like you have ordered the V2 stepped headers, whereas I bought the V1 (044931). I think the V2 don’t step out as much at the final merge so they can join to the standard s-pipe but I’m not sure if there are any differences between the primary pipe location.

You could contact SuperSprint to ask? They offered to pay to courier the headers back to Italy, so you may not be out of pocket if you already have the parts.

It is possible that SuperSprint sent me the LHD headers by mistake (there is no product number on the headers themselves), in which case your headers (and V1s) could be fine. Identifying a mix up in products could only be checked by putting two sets side by side. However, the shop that did the install mentioned they had previously seen the same problem with the V1 stepped headers, which doesn’t support that possibility.

Just had confirmation from Supersprint that the 789801 headers are compatible with RHD. Will be starting a build thread so will post up the results

Good to hear. Like TomK, I'm keen to see the results

As for the numbers Dyno Dynamics dynos produce, I'm not really sure how/if they reflect engine HP. Because of the variability of readings between days, I just gave up trying make any correlation with engine HP. I've got what I've got, so to speak

[buzyg]

As for the numbers Dyno Dynamics dynos produce, I'm not really sure how/if they reflect engine HP. Because of the variability of readings between days, I just gave up trying make any correlation with engine HP. I've got what I've got, so to speak

You also clearly have an improvement in what you had before. Which is kind of the point of an engine tune.

[///MBan]

As for the numbers Dyno Dynamics dynos produce, I'm not really sure how/if they reflect engine HP. Because of the variability of readings between days, I just gave up trying make any correlation with engine HP. I've got what I've got, so to speak

You also clearly have an improvement in what you had before. Which is kind of the point of an engine tune.

Exactly! The car has what it has, which is more than it had. Doesn’t sound very precise but the car is quantifiably quicker, feels faster and sounds better.