I'm after some hints and tips as I'm trying to work out how to reduce my spool as much as possible. My turbo is a GT3071R with a single entry 0.63 A/R hotside. It's currently hitting 1 Bar of boost at 3600rpm, where as others with the same turbo claim they are able to hit the same level of boost at 3000rpm (though I'm not sure if I've ever actually seen numbers to support their claims?)

I'm using a stock manifold, so that may not be helping things, and it has only had some mild porting work done to it to blend the ports in and remove as much of the roughness from inside the runners as practical with a Dremel and carbide bits. Similarly the head has only had some light smoothing and blending done to the runners. The only part of the exhaust setup that I can imagine would cause problems is the manifold and adaptor block have the central dividing piece still in place as originally I was running a twin-entry housing on the Garrett, and after all the hard work I put in machining the adaptor I didn't want to have to butcher it and remove the splitter. Could this be causing a 600rpm later spool though??? I personally don't believe it's enough, as the flow is divided inside the manifold as well, it's not as though it suddenly hits a restriction within the adapter block?

Another thing that occured to me is my cam timing. I'm currently running 0° on the inlet, and 4° retard on the exhaust as I find that gives a nice level of off-boost torque - however could that be effecting spool? Does anyone have any good values I could try instead to improve spool?

Thirdly is the mapping.
There seems to be two distinctly different schools of though on this. One is that you go for an overly rich mixture just pre-spool point and then pull quite a bit of timing to produce a lot of hot exhaust gas in a similar way that anti-lag works to spin the turbo up - obvious downside to this is you take power away from the engine; a mapping equivalent of robbing Peter to feed Paul.

The other tactic is to lean the mixture out (13.5:1) and feed in as much advance as you can get away with without detting which to me sounds the best approach. Any other ideas?

Hi,

understand i right, you use a twin entry exhaust hausing with a twin entry adapter?

the oem ex.manifold is not well designed for a twin-entry system, equal lengh runners are the goal

you can also try to get a high themp. difference between turbine entry and outlet (more effectiv on a single entry system)

going in direction late with the spark is also possible but you have to find the right balance as the engine itself loses tourque but you win spool up

to find the best cam timing is also good but you should go on a dyno therefor (also for the spark adjustment)

be carefull with the A/F mixture, there should be enought safety left
-> a damaged engine produces no spool up an power

what kind of boost controller do you use?
i found some nice torque by tune the BC (gain 80)

greetz

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KEEP COOL UNDER PRESSURE

street legal?.....perhaps in tschibuti

mapping :- lean it out and pull timing

Look at stock Toyota maps, stays circa 14:1 up to 4k rpm

Hmm,
lean it out & pull timing? That is a bit of a new one on me but I havent buggered with mapping for some time now and TBH Steve has overtaken me in the experience stakes.

The only mapping data I have is for an internally gated GT3071R with 0.64 A/R running on a st205 with big cams. It was only on actuator pressure ~ 0.8 bar and it got to that about 3-3.2K RPM during mapping. The only thing is that was doing a 5th gear run from 1600RPM. It didn't seem to make much diff in 2nd or 3rd though so 3600 does sound a little high.

I started mapping by running rich and safe timing and slowly leaned things out and added timing. I adopted the run it a bit lean (for a turbo car anyway) at 13.5:1 and wind in optimum timing for max power at 0.4-0.8 bar. 0.2 bar & below was considered to be lean cruise area from 2400 - 3600rpm. Above 0.8 bar I rapidly tried to enrich it back to a safe 11.5:1 with 11:1 in real high boost areas that I didn't intend on seeing! (but accidently did on a few occasions!)

The main thing I found that really sorted out early boosting was good boost controller settings. Having control for each gear made a massive improvement in response in low gears. Are you using teh Autronic for this and how much control does it currently run (logic of operation?) and is there additional settings you could apply to bring in the turbo earlier? With the clever ECU stuff now you can get fantastic response but it can take a long time to get the settings right for road use in each gear.

TBH the only thing I can suggest is to give them both a whirl and report the results You already have the theories sorted - now to figure out which one works on teh 3sgte and your turbo/setup.

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It was a twin-entry 0.84 A/R housing, it is now a 0.63 A/R single entry, but I'm still using the same adaptor.




Something which I am always scared of doing....


No boost controller at the moment, the compressor is plumbed straight into the wastegate. I forgot to mention that. I suppose a really good reduction in spool time can be achieved here as I'd guess that the wastegate starts to creep open as boost builds?

Useful info, I'll dig out a datalog later off the laptop and stick up my results of three pulls in 3d gear.



I did have it set up on the Autronic but accidentally cut the wiring to it one day and haven't re-wired it yet. I may just chuck the AVCR in for now and see how it gets on.



Yeah, the proof is in the pudding as they say!

hmmm,
Remember a wastegate starts to open way before the final pressure so it starts to bypass exhaust gases.

I originally used the AVC-R and IMHO it is the most advanced boost controller for setting up in each gear and rpm range. It is nothing on a decent ECU though. Really you want to hold the wastegate shut until as close as you can to target boost (without getting a boost spike) then set the ECU to closed loop control of duty to achieve a target boost at each load/rpm cell.

I am sure you already know all this Even the AVC-R will start to bleed some exhaust gas. Maybe try a relief valve to see what is actually possible? Then crack on with the Autronic

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Hi,

first i would added a good boost controller (ECU or stand alone BC), let me explaine you my BC

i'am using the Blitz SBC-I-Color Spec R (dual selenoid)
there are 4 channel to programm, i'am using the 1st for low boost (0,9bar)
and the other three for the map mode that runs high boost (1,1bar) (oem pistons ), with them you can write your own mapping,
the actuator of my turbo becomes no actuating pressure until 0,9bar, then a minimum and then maximum so that the boost do not overfire the engine but with a tollerance up to 1,2bar, great spool up and better driveability

this makes a true difference and possible a bigger difference on a bigger turbo

i would advise:

- added a BC
- as you have now a single entry turbo, try to become a bigger themp. difference (de-wrap the DP if he is, caramic coat the exhaust manifold and turbine housing)

i would go step by step in direction target

R&D your car

greetz

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KEEP COOL UNDER PRESSURE

street legal?.....perhaps in tschibuti

Rewiring the Autronic boostcontroller is to the ecu is one wire, the other wire is power if I'm not mistaken.

My GT3071 spools the same, for now.

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ST185 CS #1845

Sorry about the abrupt response, the phone rang so I hit submit on what I'd written


So.....

Boost control
I personally wouldn't be too dismissive of an external EBC

They provide all the early boost capability of an ECU without the requirement for a laptop to tweak them. What you do loose is reduction of boost to allow for other map parameters being out of spec. You get WAAAAAAAA boost all of the time even if the IAT sensor is saying waaaaaaa boost it more appropriate at this point in time

If you've got spare outputs then a good EBC will/should be able to look at an input and reduce peak boost based on that so you can almost get the same effect but at the expense of more rice factor.

My personal approach would be an EBC to maximise what the engine (hardware and ECU software) already has to offer. I'd expect significant reduction in spool rpm from this.

Then map/engine tweaking to maximise what is available. Finally ditch the EBC and bring control in house to the ECU and close the open loopness

As for good EBCs. The only two I have experience of and would consider good are the Greddy Profec E-01 (my favourite as I actually own one and have spent much time tweaking) and the Apexi AVC-R based on JPs trials and tribulations. Both these allow very fine rpm based control of boost. The AVC wins points on gear specific mapping but (IMO as a casual user only) looses out on usability. I know the E01 supports target/duty reduction due to external signals and I assume the AVC is the same

Sorry Sunny, I have to say that as an ex iColor user it doesn't cut the mustard for a true geek
The rpm based mapping is quite limited with only 4 rpm bands to choose from

Mapping


There's many schools of thought on this one.
I've not really tried any of them in huge detail. Before I gave up tweaking the black car (due to suspected impending piston -> bonnet interface if I pushed it much harder ) I was a little way down the lean burn late timing route

I'll be honest. I had altered my fuelling curve timing to look pretty much like the stock denso ecu timing increasing fuel to about 13:1 from 2500->3800ish when clogging it and dropping down to ~11.3:1 rapidly after this and well before peak torque/knock limit revs

The theory is that lean burn gives a hot "expandy" burn and low advance means a hot expandy burn happening in the exhaust manifold. In theory if you're on the power this gives the best results according to my research. I have to say that my results were not stellar. I think I reduced spool rpm from ~3k to 2800-2850 running 1.1 bar on a TT S148 and a completely stock engine

For reference I probably knocked 400rpm off of the spool of the stock turbo using the EBC and probably another 200 rpm off the spool time of the TT when I fitted that. I think I had the TT spooling to 1 bar at ~3krpm.
So map tweaks were somewhere around 25% as efficient as EBC tweaks. Hence my preferred route to happiness above

With Hannibal the TT spools to 1 bar by 3krpm (in 4th gear plus, in third it's all happening quite rapidly and with a stock ECU I have no logging so it's quite hard to see an exact rpm/boost curve ) all on it's own with a simple boost controller. I'm sure this is due to the better breathing and increased displacement. I'm sure I could improve it further with more tweaks to a decent highly programmable EBC

The other popular school is the low advance high fuel approach to almost achieve antilag with the engine coming on boost. I've not done any practical research into it but scouring books and the net tends to hint towards this not being totally effective. It's a great strategy when there's no airflow with the throttle closed. In fact it's about the only option you have in these circumstances. You create an explosive fuel mix with what resources you have - a little bit of air and a lot of fuel. However research seems to indicate that a "correct" lean burn combustion event will contain more energy than an "eat this" antilag type combustion event and hence should spool the turbo sooner

I'd really like to see practical figures for both strategies. I'd feel happier with the loads-a-fuel antilag approach if the figures were similar to the lean burn approach as it's got to be better for the engine. I can't help but think that the exhaust valves will suffer in a road car on track environment when faced with repeated excursions into the f.hot exhaust gas spool area of a lean burn map

Hi,

i agree, 4 channels are a bit to less but i'am happy

greetz

_________________
KEEP COOL UNDER PRESSURE

street legal?.....perhaps in tschibuti

Indeed.

Fine for most normal people

What dyno curves don't tell you is the 'time delay' side of the 'lag' i.e. what power you get for the first second after flooring it. This is what makes for drivability & throttle response. I would tend to favour a map which gives good torque with little boost over one which sacrifices efficiency in order to get boost a bit lower - after all, if you've got time to wait then you've got time to drop a gear so low RPM boost doesn't matter anyway.

Fair call Chris. The problem with retarding timing and a rich fuel mixture is that you will lose lots of power in the region where it is spooling followed by a "whack up the whooper" as it reaches pressure and you revert to decent AFRs and MBT. What you gain in earlier spool I suspect you will lose in time whilst it is spooling.

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