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Decel spark for snap, crackle and pops !


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Hi All , been mucking with my Wife’s Territory. I’ve got it tuned to 14 psi . Pretty much the limit of the NA btr box with 365 k on the box . Motor has 10 k on on it after rebuild . 

I was watching Bobby McBoost utube Chanel and he had his car set to retarted spark on decel and made some cool backfires ! 
so I wanted to do the same on my test mule , aka the Wife’s shopping trolley! 

Bit of a recap . So I’m a plumber, built a turbo Barra in my shed with 2 Nd hand rods and turbo pistons (3r 23 aa rods).

I hand ported an fg head with Fg cams , the usual cam springs , head studs and oil gears .  Stuffed the first build with ring gaps being cut wrong . Learnt how to do it properly and rebuilt again!
Now , 20 thou top ring , 22 thou bottom ring . 2nd time used a proper cutter and only cut one side ( watch tube !) . 1000 cc injectors into an fg NA manifold. 

Ok so I flashed pretty much -5 on decel and got some nice crackles on 98 and a few pops , which be quite interesting at night ! Going to go another-5 to see what happens  and that will do . As you reportedly can blow mufflers apart ! So easy does it ! 

Bobby bloke , mentioned also about delaying fuel cutoff in fuel cut costing? 

I haven’t worked that one out yet . So if anyone knows , please chime in ! 

regards Graham.
Ps so wrapped with my tune . Have tuned the btr box and have it just sweet and just getting the fuelling right has taken must be nearly 50 flashes ( including gearbox) . Something that is just impossible in a 2 hour tuning session. Especially for an odd bod Na conversion. The b series Na pcm is sort of at its limit at 14-16 pound with the limited 1.2 timing table mho. 



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Ok thanks heaps Roland I’ll look at . I’m very much learning! 

just a bit of encouragement to those up to their armpits in Barra and losing parts in the “ Barra Triangle!” 

Now I’m on the other side of the Barra Hurt locker !! Building and tuning my own Turbo Barra has been an absolute ball! There have been times thinking of “ what am I doing “ so glad I saw it through . 
it sounds so good when my Wife gets under it when I’m outside the car ! ( She loves driving it and chopping b triples and caravans ! Even though she doesn’t admit it lol!) 

you can here the wuhan war whistle Gt 3576 screaming away . The induction noise of that turbo sucking like a jet engine and just a sweet exhaust note going through the 4” dump and 90 mm cat and 3” duel straight throughs ( middle and end muffler, single exhaust)! 
Yep big smiles and worth all the pain !! 

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this has been discussed over on this thread.

I have left my e85 drifto ute on around 6-8 degree alternating on decel and it cracks nice, being manual it will crackle often, its also straight through exhaust.

I have my daily turbo terry on around 8-10 deg alternations and it will crackle a little bit on in gear-decel, but you need to have it in manual mode for this otherwise the zf will just change gear and you wont get any pops - but im fine with this as its a daily and has a 4inch dump/cat and 3.5inch system with a hotdog and a muffler.

I have a r31 with a bf na and zf, the exhaust is straight through with a single hotdog....it sounds like a general heap of crap over 1500 rpm. I experimented with decel timing and additional fuel but in the end put it more like the territory around 10 deg as it would be a bit obnoxious with low timing and additional fuel.


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