BPU made no difference to bhp or torque

[Mont]

When I bought my Supra late last year I took it to my local dyno to get a base reading which resulted in 289bhp and 278lb ft. After carrying out BPU mods my results today from the same dyno are 288bhp and 273lb ft.

 

The car is a J-spec 1995 twin turbo and at the first run the only modification over standard was a Blitz Nurspec catback.

 

Since then I've fitted:

- Whifbitz decats - both 1st and 2nd

- Whifbitz restrictor ring

- Copper plugs at 0.7mm

- Walbro fuel pump

- Chris Wilson Fuel Cut Defender

- AEM Failsafe boost/AFR gauge

 

I took the car back to the same dyno today, more for a health check to make sure things are running ok after making these changes, but obviously also keen to see what gains I've made, and was a bit surprised to see the results are pretty much exactly the same as before the whole way through the run. I thought there'd even be some sort of differences, even at certain points of the graph! Can anyone think of any explanation as to why this might be?

 

My first thoughts are that there is another restriction somewhere. The Blitz catback looks to be pretty much unbaffled so don't think it's something there. The only other thing I can think of doing would be to remove the restrictor ring and take it for a run to see if it boosts any higher, but would prefer not to do that given the risks involved. Any other place where another restriction might be? Thanks.

 

Boost readings are consistently reaching 0.7bar, with a quick peak at 0.8bar, so pretty much same as standard.

 

I've attached my dyno sheet below which shows both my run from last year and the run from today. The one with jagged lines was from the first run last year which the dyno guy says may be have some previous interference on the roller.

 

Edited August 31, 2018 by Mont (see edit history)

[DaveR]

It’s in the setup. As well as what you’ve done, BPU also includes raising the stock boost to around 1.2 bar (with an electronic boost controller usually) to maximise the effect from the turbos to create more power. If boost is constant, so is power, hence no gains.

[Ric]

The boost makes the power.

 

So if you are only getting 0.7bar of boost your restrictor ring needs opening up slightly (unsafe way) as its easy to get this wrong and overboost if you cut too much out.

 

OR fit a boost controller, now that the cats are removed only the restrictor ring is holding back the turbos, pushing the boost up with a controller is generally regarded as the safest way.

[Dim Sum]

http://www.mkivsupra.net/vbb/showthread.php?94705-BPU-(Basic-Performance-Upgrade)

 

I link for full information on BPU

 

Also what other members have mentioned you need to raise the boost to actually benefit from the BPU.

 

If money ain't a issue I would get a electrical boost controller to monitor boost level and that way you can adjust in a touch of a button.

[Mont]

http://www.mkivsupra.net/vbb/showthread.php?94705-BPU-(Basic-Performance-Upgrade)

 

I link for full information on BPU

 

Also what other members have mentioned you need to raise the boost to actually benefit from the BPU.

 

If money ain't a issue I would get a electrical boost controller to monitor boost level and that way you can adjust in a touch of a button.

 

Thanks for the replies so far.

 

That's the link I'd used for the basis of the parts for my BPU and I took from it that removing the restrictive cats would increase boost, with the restrictor ring installed to bring boost pressure down enough to stop the ceramic blades coming off the turbo. It also reads from that link that BPU'd UK cars will still only boost to 0.85bar due to the bigger wastegate and so that's why they need a boost controller to increase boost above that. I'm def taking on board that a boost controller should help me, however that link seems to say that all that I needed to raise boost pressure on a Jspec car above standard were the parts that I'd installed. Have I read this wrong somehow?

 

 

In both Jspec and export spec, BPU will raise engine power to around 400bhp. Not only will it release more power but it allows much quicker turbo spool-up, which vastly increases drivability.

 

How it works

In stock form, the boost pressure the turbos produce is controlled by back pressure in the exhaust system (I.e. highly restrictive catalytic converters and exhaust system). There are two approaches to BPU dependant on the model of car; as such the next section is split between Jspec and Export spec:

 

 

Fundamentals of BPU

 

Jspec:

To raise boost beyond the stock level the restrictive catalytic converters are removed, thus allowing the turbos to spin faster and produce more boost pressure.

 

A properly sized restrictor should bring the maximum boost pressure down to 1.2 bar or less.

 

Parts required:

 

Obviously all that’s needed to raise the boost pressure is a double decat & restrictor ring (Jspec) or double decat & boost controller (export spec). However, it will not work without further modifications. The following will be required in both models:

 

1) Aftermarket cat-back exhaust

 

2) Fuel cut defender

 

 

3) Updated fuel pump

 

 

4) Colder grade spark plug

 

 

I do understand that I've essentially removed two restrictions (the cats) and installed another restriction (the restrictor ring) however it's all about the flow with turbo cars and so I thought the increased flow from the decats with some control from a restrictor ring would have at least provided some improvements when comparing both runs on the graph.

 

So it's a boost controller needed or experimentation with the RR. Thanks again.

Edited August 31, 2018 by Mont (see edit history)

[ellis]

I'd just fit a 1.1 or 1.2 RR - job done

[Dim Sum]

I'd would go straight to a boost controller if I'm honest. Also you can just buy a restrictor ring set for 1.2 bars and saves you messing around with sanding the RR

 

- - - Updated - - -

 

That way you can monitor the boost as well

[Scooter]

I think the rings come in a conservative diameter. So the sellers don't get blamed for breaking turbos the first time out.

 

It'll vary car to car given the exhausts and general state of the car etc.

 

I had a malfunctioning boost controller on my car when I got it and so disconnected it, ran it to see peak boost and then spent a few goes of removing/refitting it and filing it out inbetween until I got to approx 1.15bar (it's not an exact science). Whip it out, hopefully it's on one of the second cat joints and then draw a felt tip line around the inner diameter and dremel etc off til the line goes (go small first til you get a feel for how it's effecting the boost) I 'think' a mm or two all the way round won't see it jump up too much but my memory is hazy. Bit of a faff (easier if you have a peak hold boost gauge) but only need to do it once.

 

This suits me fine, others want to have varying boost settings. In my opinion, whilst it probably doesn't make that much difference, I wouldn't want a system that restricts to 0.7 bar being controlled up to 1.2, I'd get the ring a bit opened up at least so you get to say 0.9/1.0bar.

[samdale]

Surprised no one else has said yet, but doing any of the above is just masking a problem.

 

With what you have, you should definitely be getting more boost. Ask yourself why you're not getting the expected boost, not what else you can do to get more.

 

Are both turbos coming online?

[The Raven]

Ok im going for a VSV issue stopping number 2 coming in or the link pipe between 1 and 2 has internally collapsed causing the restriction.

 

I am however a fool so this may not be the case

[Ric]

Surprised no one else has said yet, but doing any of the above is just masking a problem.

 

With what you have, you should definitely be getting more boost. Ask yourself why you're not getting the expected boost, not what else you can do to get more.

 

Are both turbos coming online?

 

Why should he? if the RR is a 0.7 bar RR he wont get anything extra?

 

If he opens up the RR larger and it's stil 0.7 bar there is a problem.

 

It's not VSV related or anything else, 0.7 is FULL stock pressure, if the VSV for the 2nd turbo was dead he wouldn't get anything over 0.5 bar

 

Let's not spread worry for no reason.

[Rob W]

The RR must be small to be getting 0.7bar, as stated open it up slightly.

 

You want to be aiming for around 1bar with just the RR in place, then with a boost controller raise to around 1.1-1.2bar. I would not just go chucking on a boost controller to try and raise the boost as your exhaust temps will be very high.

Edited August 31, 2018 by Rob W (see edit history)

[Mont]

Both turbos are def working. The dyno graph shows the second turbo at 4,000rpm.

 

I gave Whifbitz a call this afternoon about the restrictor ring and he couldn’t be more helpful. It’s a 1bar rr for all the bpu mods plus a bigger intercooler, which I don’t have. He suggested the same as above; Boost controller or experiment with the restrictor ring.

 

Ideally I only really want about 1bar as I still want to play safe with the turbos.

Edited August 31, 2018 by Mont (see edit history)

[samdale]

Why should he? if the RR is a 0.7 bar RR he wont get anything extra?

 

If he opens up the RR larger and it's stil 0.7 bar there is a problem.

 

It's not VSV related or anything else, 0.7 is FULL stock pressure, if the VSV for the 2nd turbo was dead he wouldn't get anything over 0.5 bar

 

Let's not spread worry for no reason.

How bad do we think the tolerances are on the whifbitz 1bar restrictor ring? I just can't see it being that far off so filing that out may just mask a pre-existing issue.

 

 

[Ric]

How bad do we think the tolerances are on the whifbitz 1bar restrictor ring? I just can't see it being that far off so filing that out may just mask a pre-existing issue.

 

/QUOTE]

 

Mask what issue? it's boosting 0.7.. stock, perfect, factory boost? before and after the mods.

 

As somebody has said, every car is different just because a 1bar ring might work on your car it might not on another.

Edited August 31, 2018 by Ric (see edit history)

[samdale]

Mask what issue? it's boosting 0.7.. stock, perfect, factory boost?

 

As somebody has said, every car is different just because a 1bar ring might work on your car it might not on another.

How much more free flowing is the RR than the cats? It's a bit of a coincidence that it provides EXACTLY the same resistance non?

 

 

[Ric]

How much more free flowing is the RR than the cats? It's a bit of a coincidence that it provides EXACTLY the same resistance non?

 

because thats the size they are made at..

 

The hole is usually around 2inch in diameter inside a RR which "should" give around 0.9/1bar

 

Cat's and their joiners are 3 or 3.5" stock, so yeah, you're restricting it quite a lot (around the same as the cats would)

[samdale]

because thats the size they are made at..

 

The hole is usually around 2inch in diameter inside a RR which "should" give around 0.9/1bar

 

Cat's and their joiners are 3 or 3.5" stock, so yeah, you're restricting it quite a lot (around the same as the cats would)

I guess in my head I look at a cat and just picture it as a tiny open area. Whereas the RR looks like a "big" hole.

 

 

[X13mgr]

Forget bpu. We all bin there. Lol. Go single

Other wise ye slightly. And I mean slightly 5mm all round would be your limit. On opening up the rr

[Dim Sum]

Forget bpu. We all bin there. Lol. Go single ��

Other wise ye slightly. And I mean slightly 5mm all round would be your limit. On opening up the rr

 

Go single and a huge price in differences from BPU

[X13mgr]

Yes dim the price difference is massive buts it’s the best difference I ever spent. Having bin bpu for 3/4 years. I got the bug for more power.

[nigelboyne]

Hardly the fuel cut not wired in properly? Or the copper plugs? Bpu really transforms the car you should see 60to70hp gain when your boosting to 1.1/1.2bar

Edited August 31, 2018 by nigelboyne (see edit history)

[Scooter]

As long as you are very cautious you could just remove the ring altogether and then go for a careful drive and see if it is a changed animal, it should be obvious. If it is boosting better then things are normal and you know the ring is just too small.

 

This would require restraint and part throttle (no sustained planting the throttle) and perhaps a helper to view your boost gauge if you haven't got a settable audible warning.

[Dim Sum]

Yes dim the price difference is massive buts it’s the best difference I ever spent. Having bin bpu for 3/4 years. I got the bug for more power.

 

I know what you mean hence why I'm single turbo too. But thought the OP might want to achieve BPU before deciding to go single.

[Homer]

It looks like there might be a turbo or wastegate problem from that dyno graph, it shouldn't look like that.

 

As long as you are very cautious you could just remove the ring altogether and then go for a careful drive and see if it is a changed animal, it should be obvious. If it is boosting better then things are normal and you know the ring is just too small.

 

This would require restraint and part throttle (no sustained planting the throttle) and perhaps a helper to view your boost gauge if you haven't got a settable audible warning.

 

Fully agree with Scooter's approach, but it's essential to re-iterate "cautious"! If the turbo's are working well you'll see 1.6 bar immediately after 4k rpm but you should back off as soon as the boost starts hitting 1.2 bar. Above that is potential detonation territory. It's just a test and only do it once.

 

One that's checked, you'll know both turbo's are working. If it hits high boost then it's a restriction problem.

 

I disagree with others who have said to fit a boost controller, it adds nothing to a jspec with BPU mods (UK/Euro models are a different). They're only useful once exhaust restrictions are reduced to the minimum required level.