chip help

[UK-typhoon]

hi guys,
im from london england, and a friend of mine has a typhoon and we are working to improve it, it was bought already modified, stainless steel downpipe and exhaust, air box removed, battery moved to the boot, last year we ran it at the local drag strip and it ran 12.7. looking to improve upon this, the trucks previous owner included an stg chip, gauge style controller for the chip, 3 bar map sensor, uprated fuel pump all to be fitted that he hadnt had time to do. recently fitted all these items, plus a few others (msd 6btm, boost gauge, 3200 rpm torque convertor (too high i know, but he got it new for free and wanted it fitted) and an adjustable fuel pressure regulator, the truck started and runs fine, and drives good, but when you try and accelerate hard from a stand still it builds 12 pounds of boost then the engine splutters and drops down to idle speed. this weekend was at the track and still unable to find the problem, the fuel pressure was set at 50 psi with the reference pipe off and 45 psi with it on, and the truck seemed to be smoking, so lowered the fuel pressure to 40psi with the pipe on and that seemed to cure the smoking, but it still spluttered. trying to find the problem it was decided to re install the stock chip, done that and the car accelerates strong from a stand still with no splutter. we ran the truck with the stock chip back in it and it ran a 13.9 quarter mile, quite a bit off from last year, there was also a stock typhoon at the track running 14.1 - 14.0 quarters, what could have been done to the truck by previous owners to cause the truck to be over a second quicker than stock last year?
what i want to know, does this mean the stg chip is faulty? or is there another problem? i've been tuing carbed chevy V8s for years, but have little experience but a basic knowledge of fuel injection

thanks for your help

 

[dgoodhue]

Re: chip help

You have a vacuum problem if the FP is only dropping 5 psi with the regulator attached. It should drop about 10 psi. I would replace your vacuum line if you haven't done so.

The STG Ultimate chip is a lot harder on ignition parts. Do you have tach flutter?

 

[UK-typhoon]

Re: chip help

ok, i will look into the vac problem. what vacuum should the engine have at idle roughly?
recently fitted a msd ignition system and a set of taylor leads. what plugs would you reccomend and what gap?
no tach flutter

 

[dgoodhue]

Re: chip help

It should be about 20in-hg.

 

[UK-typhoon]

Re: chip help

ok, i will check that. any ideas what would make the truck run over a second quicker thatn stock with no real obvious modifications, apart from stainless steel downpipe and exhaust system?

 

[Tooky]

Re: chip help

I wrote a website with two pages that go to great lengths explaining exactly how you can lose a full second of time on a stock truck. Check them out:

How to Get Your Stock Truck Deep in the 13's ...Without Buying Hardly Anything

Key Ingredients to a Fast Truck
<--- The top of this page has an explanation of exactly how and why your stock "280 HP" truck could be operating at as low as 140 HP.

 

[UK-typhoon]

Re: chip help

i have looked on the site and i found it very helpful for future tuning ideas

but what i am asking is, the only obvious modifications to the car are stainless downpipe and exhaust system, cone air filter and removal of the A/C, i'm fairly sure these mods alone would not make the truck run the 12.7 quarter mile it did last year, so, what non obvious mods could have been done to the truck to make it run that?

thanks

kay

 

[turbodig]

Re: chip help

i have looked on the site and i found it very helpful for future tuning ideas

but what i am asking is, the only obvious modifications to the car are stainless downpipe and exhaust system, cone air filter and removal of the A/C, i'm fairly sure these mods alone would not make the truck run the 12.7 quarter mile it did last year, so, what non obvious mods could have been done to the truck to make it run that?

thanks

kay

Actually, they could very well have. I've had several trucks here that ran mid-high 12s with fewer modifications.

Lots of boost, a good sticky track, and a good launch... it's not unreasonable.

 

[Tooky]

Re: chip help

i have looked on the site and i found it very helpful for future tuning ideas

but what i am asking is, the only obvious modifications to the car are stainless downpipe and exhaust system, cone air filter and removal of the A/C, i'm fairly sure these mods alone would not make the truck run the 12.7 quarter mile it did last year, so, what non obvious mods could have been done to the truck to make it run that?

thanks

kay

I don't think you're understanding what I wrote on my site and what I'm trying to explain. It's not about how many mods you have or don't have. It's about analyzing and collecting data to observe the engine's performance directly, and making necessary adjustments to see that the engine produces maximum power output. I got my truck with a stock turbo, full A/C and everything else, to run 12.26 @ 108 MPH, stock downpipe, etc.

It's a lot more complicated than adding up a simple list of mods and thinking it should result in a specific ET. There are hundreds of things that can go wrong on any SyTy (stock or modified) and every truck has at least a few issues. It's up to you to scrutinize the truck and locate where your performance bottlenecks lie.