jlundin22

I just put a rear mount turbo on my 1988 c4 L-98 i'm going to run 6psi of boost. I am not sure what the timing should be and how to control it i don't want to spend a ton of money on stand alone computer system.

jlundin22

Come on guy's no one has anything!!!!!!

JoBy

The easy way is to set the base timing a few degrees later. ( turning the distributor ).
The downside is that you will be running less timing than optimal most of the time.

QuickGlass

Are you running 93 octane?
I would start with the total timing at around 20 degrees.
Then watch for knock retard on a scanner and adjust accordingly.

You can use a boost retard. Set it for 2.5 degrees per psi.

How are you adding fuel?

jlundin22

yes I'm running 93, If I run a retard box can I give it more total timing so it's not such a dog untill the boost kicks in then the box will take it away? I"m running 225 walbro pump, stock ls1 injectors and adjustable fuel reg. set at 58psi.

tequilaboy

The good news is that it is possible to run a turbo with a stock 165 ecm with supporting hardware and specialized tuning, however it is not a minor undertaking. An aftermarket stand alone ecm and boost retard module should not be necessary.

Here's what would be needed to do so:

Tuning and datalogging capability.
Sufficiently sized injectors for the expected power and bsfc (I'd expect 42 lb injectors at minimum).
A MAF sensor that is capable of measuring all of the expected airflow.
Manual boost controller (assumed)
Custom tuning that includes the following items:

• range extension, signal processing and calibration for appropriate MAF
• pw range extension to support rich AFR targets
• LV8 calibration to support boost.
• Spark advance tailored for extended LV8 range to provide boost spark control
• LV8 dependent AFR targetting in PE mode to properly fuel both in and out of boost independent of rpm
• Timing safeguards for excessive IAT.
• Patience and know-how to make it work (hint-hint).

BlowerWorks

YUP ! TequilaBoy has it nailed ! LOL Read some old posts and you'll see that BlowerWorks can easily take care of you - with Real Time Tuning using Moates and Tunerpro RT.
greg

QuickGlass

I also agree with tequilaboy. That is the best method.

But if you still want to keep it in expensive, using an 8:1 FMU and boost retard will work. You can then keep your LS1 injectors (Probably 28lb/hr@58psi).

It is still a must to have a way to data log and modify the tune.
You have to start with the fuel rich and low timing.
Get the fuel set 1st while also making sure there is no knock.
Then bring the timing back until just below knock.

Keep it safe. It's better to lose some power then lose an engine.

jlundin22

I have not ran the car yet I'm just finishing up the turbo's oil return system then the car will be ready to run. I have a data logging wideband installed what is a safe AFR to start with. I've heard alot about 20-22 total timing being where I should be, what do you think ?
Also what would unsafe IAT's be considered?

tequilaboy

Regarding unsafe IAT's:

The answer is totally dependent upon timing, compression ratio, boost and fuel and/or presence of internal coolants like water and methanol.

With intercooling, I don't like to see IAT's over 120F. With hot boost, you may see 250-300 F. Both can be made to work, but increased IATs always means increased detonation risk and likely means reduced power.

Its all about making the right compromises for a given combination. Either tune for the worst case conditions or make the tune adaptable for all conditions.

jlundin22

got car running it's a monster just waiting on the Blowerworks custom eprom then it should really come to life!!!

boostedmaxPSI

Any updates?

jlundin22

sorry I've been busy with the holidays, the car is running great i'm so impressed with blowerwork and their knowledge. If anyone has any tuning or boosted needs I highly recommend using BlowerWorks they're top notch!! I turned the boost up to 8 psi. and the w/b stays around 11 to 11.5. any advice on max boost for a stock engine?

nothing feels better than a boosted vette!!

Tom400CFI

Cool to hear that it's running well, and that you're happy with it!

What turbo charger did you select for this application?

jlundin22

HX 35 Holset, the car feels good and i'm wondering if it's time for the dyno?

boostedmaxPSI

My chip is in the mail now. Graig has been great to work with. We are taking baby steps now and making some minor tweaks first then we will start the actual tune process.

I'm currently running 16psi however, my compression ratio is 7.5:1.

BlowerWorks

Hi Jl !
Thank you for the 'cudos' !!!! After almost 30 years I wake up seeing all the bolts in the engine compartment !!! LOL However, all credit for the 'miraculous' tunes and the development of my slot style MAF sensor must go to TequilaBoy. He's an engineers'
engineer !!! He splits hairs I'm not even aware of and as such can tweak a C4 like nobody else can - period !!! Thanks again - greg